OBD-II Mega list

Got a diagnostic trouble code and want to know what it it?

This post covers OBD2 Codes divided into 4 groups: 1-Powertrain – Pxxx, 2-Network – Uxxx, 3-Body – Bxxx, and 4-Chassis – Cxxx). You will also find their meanings, causes, symptoms, and how to fix them. We also offer a free codes list for download.

Meaning and Fix guide of OBD2 codes — OBD2 Codes Meaning & Fix Guide

Table of Contents [show]

What is an OBDII Code?

obd2 codes samples — Samples of OBD2 Codes detected with OBD Auto Doctor software

OBD is short for onboard diagnostics. It refers to a vehicle’s electronic system that performs self-diagnosis and reporting. Whenever a problem is detected the system records it as a unique code. That code is known as a diagnostic trouble code (DTC). As a vehicle owner or mechanic, you can pull that code and interpret it to understand the nature of the problem. For example, if the car gives you the P0201 code, it means that there’s a malfunction in cylinder 1 of the injector circuit. Your job is to pinpoint the issue and fix it.

Now, with that in mind, OBDII codes are trouble codes specific to OBD2 vehicles. These are generally cars, SUVs, light trucks, etc. that are made and/or sold in the US since 1996. In other words, if a car is a 1996 or newer model, it is OBD2-compliant. And that also means that it uses OBD-II codes to do self-diagnosis and reporting.

I’ll be using all three interchangeably all through the post, be sure not to get confused.

How to Interpret the Letters and Digits in an OBD2 Code?

OBD provides monitoring for various systems. They include the engine control module, body, chassis, etc. When you look at the code, you can immediately tell which system has a fault-based on how it appears.

Here’s a breakdown.

The First Character (Letter)

All OBDII codes start with a letter that denotes the part of the vehicle that has a fault. Let’s look at each letter, shall we?
P – Powertrain. It includes the engine, transmission and all the associated accessories.
U – Network & Vehicle Integration. These are functions that are managed and shared by onboard computer systems.
B – Body. These are parts mainly found in the passenger compartment area.
C – Chassis. It covers mechanical systems and functions like steering, suspension, and braking.

The Second Character (Number)

The first letter is usually followed by a number. This number can only be ‘0’ or ‘1’.
0 – If it’s a ‘0’, ‘2’, or ‘3’ then the code is a standardized (SAE) code; also known as generic code
1 – If it’s a ‘1’ then you’re looking at a manufacturer-specific code

The Third Character (Number/Letter)

This number denotes the particular vehicle system that has a fault. There are eight systems in total:
0 – Fuel and air metering and auxiliary emission controls
1 – Fuel and air metering
2 – Fuel and air metering (injector circuit)
3 – Ignition systems or misfires
4 – Auxiliary emission controls
5 – Vehicle speed control and idle control systems
6 – Computer and output circuit
7 – Transmission

A-F – Hybrid Trouble Codes

The Fourth And Fifth Characters (Number)

The final piece of a DTC is a two-digit number. This number defines the exact problem that you’re dealing with. It can be any number between 0 and 99.
As you can see a typical DTC has five characters in total, and each one of those characters gives it a description. For example, if you get the code P0219, it means that the car has an engine over-speed condition.

The ‘P’ means that the problem is in the powertrain. The ‘0’ means that it’s a generic code while the ‘2’ refers to the fuel and air metering (injector circuit) system. The last two digits (19) define the problem; i.e., an over-speed condition.

Want to know more about codes and their meanings? Below comes a more comprehensive OBD codes list.

As mentioned already, DTC codes that start with ‘P’ relate to the powertrain. Those that start with ‘U’ are for the network and vehicle integration system. Codes whose first character is ‘B’ relate to the vehicle’s body while ‘C’ codes are for the chassis.

OBD2 Codes List for FREE Download

Generic Powertrain OBD2 Trouble Codes

Generic Chassis, Network, and Body Codes

Manufacturer-Specific Codes

OBD2 Codes: Meaning, Causes, and Fixes

Below comes the details of all OBDII codes.

But if you want to find your codes right away, jump to the appropriate code lists that contains meaning, symptoms, causes, and fixes!!

P0010 Intake Camshaft Position Actuator Circuit / Open (Bank 1)

The P0010 code happens when bank 1 camshaft and the crankshaft have a variation in mechanical timing. The problem occurs when the engine experiences high RPM. The ECM doesn’t properly adjust valve lift at high RPM.

Main Symptoms:

Check Engine Light comes on
Engine performs poorly at high RPM
Car runs roughly
Lower fuel economy
Car fails emission test

Possible Causes:

Sludge in engine oil
Faulty OVC (oil control valve)
Internal damage to ECM
ECM timing is out of sync
Wiring damage
Malfunction of crankshaft or camshaft sensor
A short in VCT/VVT circuit, or the circuit is open

Diagnostic Steps:

Use an advanced diagnostic tool to pull engine codes
Inspect the VVT/VCT solenoid system for dirty oil
Inspect the circuit for wiring problems

P0011 Intake Camshaft Position Timing – Over-Advanced (Bank 1)

The P0011 code is triggered when the camshaft timing for bank 1 is above and beyond the limit set by the ECM. This causes an over-advanced condition that occurs either during retarding or advancing of the camshaft timing.

Main Symptoms:

Check Engine Light comes on
Hard starting
Poor idle
Car may run rough or stall
Poor fuel economy
Car may fail emission test

Possible Causes:

Camshaft remains advanced despite ECM commanding it to retard
Bank 1 oil control solenoid may be clogged or stuck
Oil may be too thick and is thus blocking passages in bank 1
Wiring problems in VCT/VVT
Oil continuously flows to VCT piston chambers open

Diagnostic Steps:

Check that engine oil is clean and has the recommended viscosity
Visually inspect wiring in the CVT system
Pull engine codes and live data using advanced diagnostic tool

P0012 Intake Camshaft Position Timing – Over-Retarded (Bank 1)

The P0012 code is triggered when bank 1 is having an over-retarded timing condition that occurs either during retarding or advancing.

Main Symptoms:

Check Engine Light comes on
Hard starting
Poor fuel economy
Car may run rough or stall
Car may fail emission test

Possible Causes:

Camshaft timing is incorrect
Wiring problems in VCT/VVT
Oil continuously flows to VCT piston chamber
Timing valve solenoid control has failed and is stuck in open position
Oil may be too thick and is thus blocking passages in bank 1

Diagnostic Steps:

Check that engine oil is clean
Visually inspect wiring in the CVT system
Pull engine codes and live data using advanced diagnostic tool
Using bidirectional scanner, command the timing valve solenoid control valve to open and close then see if camshaft timings change. If they change it means the valve is not the problem

P0014 Exhaust Camshaft Position Timing – Over-Advanced (Bank 1)

The P0014 code happens when bank 1 camshaft is having an over-advanced timing condition that occurs either during retarding or advancing.

Main Symptoms:

Check Engine Light comes on
Hard starting
Poor fuel economy
Car may run rough or stall
Car may fail emission test

Possible Causes:

Camshaft timing is incorrect
Wiring problems in VCT/VVT
Oil continuously flows to VCT piston chamber
Timing valve solenoid control has failed and is stuck in open position
Oil may be too thick and is thus blocking passages in bank 1

Diagnostic Steps:

Check that engine oil is clean and full in the tank
Visually inspect wiring in the CVT system
Pull engine codes and live data using advanced diagnostic tool
Using bidirectional scanner, command the timing valve solenoid control valve to open and close then see if camshaft timings change. If they change it means the valve is not the problem

P0016 Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A

The P0016 code occurs when the crankshaft and camshaft signals are out of time. Meaning the ECM can detect that the timing of the crankshaft and that of the camshaft do not correlate.

Main Symptoms:

Check Engine Light comes on
Engine may crank but fail to start
Engine may continue to run but will record poor performance
Rattling sound in the harmonic balancer
Poor fuel economy

Possible Causes:

Timing chain is overstretched
Tone ring on camshaft and/or crankshaft is has slipped or broken
Timing chain has jumped teeth and put camshaft timing out of position
Problems with camshaft phaser and putting the phaser out of position
Wiring to crank/cam sensor is damaged

Diagnostic Steps:

Inspect oil control valve (OCV) for connection or wiring problems
Check that engine oil is clean, full and has correct viscosity
Pull engine codes and live data using advanced diagnostic tool
Using bidirectional scanner, command the OVC on and off then see if camshaft timings change. If they change it means the valve is not the problem

P0037 Heated Oxygen Sensor (H02S) Heater Control Circuit Bank 1 Sensor 2

The P0037 code is triggered when bank 1, sensor 2 of the O2 sensor heater circuit is faulty. As such, the engine isn’t achieving closed loop and therefore the car has increased emissions.

Main Symptoms:

Check Engine Light comes on
Longer time needed to achieve closed loop
Decreased fuel economy
Engine may go into fixed fuel mix

Possible Causes:

H02S sensor in bank 1, circuit 2 is not sending the correct signal to ECM
Damaged or failed element in heater circuit
Open in O2 sensor heater’s circuit
Open/short in O2 sensor heater’s battery
Defective ECM (this is the least likely cause)

Diagnostic Steps:

Inspect wiring and power to the O2 sensor and ensure there’s no damage/open/short
Use code reader to pull engine codes
Check voltage of O2 sensor and ensure it matches manufacturer’s specs
Replace O2 sensor if necessary

P0102 Mass or Volume Air Flow Circuit low Input

The P0102 code happens when the mass airflow (MAF) sensor is not performing within the normal expectation and is therefore sending a lower signal than normal (due to low voltage).

Main Symptoms:

Check Engine Light comes on
Extremely low fuel consumption and thus internal engine problems
Engine runs roughly
Car idles and stalls frequently

Possible Causes:

Defective MAF sensor
Presence of dirt and debris in MAF (restricts airflow)
Leaks in air intake system
Improper wiring of the circuit to MAF sensor

Diagnostic Steps:

Use code reader to pull engine codes
Visually inspect MAF sensor wiring and circuit
Check for air leaks in air intake system
Inspect MAF to see if there’s dirt and debris

P0106 Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem

The P0106 code is triggered when the Powertrain Control Module (PCM) has not detected a change in engine speed, throttle angle and/or exhaust gas recirculation (EGR) despite an increase in manifold absolute pressure (MAP). Increase in MAP indicates increase in engine load.

Main Symptoms:

Check Engine Light comes on
Poor fuel economy
Engine fails to idle
Engine produces black smoke (visible at tailpipe)
Erratic acceleration

Possible Causes:

Faulty MAP sensor
Air intake component is loose, cracked or doesn’t have its plastic fitting
Water or dirt affecting connector to MAP sensor
Corrosion may be causing poor signal to and from MAP sensor
PCM is defective (least likely but not unlikely)

Diagnostic Steps:

Use an advanced scanner to pull engine codes
With that scanner, take the reading of MAP sensor when engine is off but key is on. It should be similar or close to barometric pressure (BARO) reading
Start the engine and see if MAP sensor readings drop significantly. If they do the sensor is working properly

P0113 Intake Air Temperature Circuit High Input (Sensor 1)

P0113 means that the signal voltage from the intake air temperature (IAT) is above 5V, which is more than the expected range.

Main Symptoms:

Check Engine Light comes on
Engine may run extra lean

Possible Causes:

Defective IAT sensor
Loose or faulty wiring at IAT sensor
Open or short in IAT ground circuit, signal circuit or reference circuit
PCM is defective (least likely but not unlikely)

Diagnostic Steps:

Use an advanced scanner to pull engine codes.
View live data from the IAT sensor. If the reading is less than -30 degrees then the sensor is likely to be faulty. If otherwise then it’s probably an intermittent problem
Check the wiring for opens and loose connections

P0118 Engine Coolant Temperature Circuit High Input

P0118 means that the PCM has determined that ECT is less than freezing temp yet the engine has been running for several minutes, which shouldn’t happen.

Main Symptoms:

Check Engine Light comes on
Poor fuel economy
Engine fails to idle and may not start completely
Engine produces black smoke (visible at tailpipe)

Possible Causes:

Defective ECT sensor
Open or short in ECT signal or ground circuit
PCM is defective (least likely but not unlikely)

Diagnostic Steps:

Using an OBD2 scanner, check the reading of ECT. If it’s a logical reading then the problem is intermittent
Perform a wiggle test while looking out for drop-outs. If there are any then there’s a bad connection to or from the ECT sensor

P0121 Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance Problem

P0121 happens when the PCM has detected that the throttle position sensor (TPS) voltage is more or less than it should be for the current RPM.

Main Symptoms:

Check Engine Light comes on
Car produces black smoke (visible at tailpipe)
Car stumbles when you accelerate or decelerate
Engine may fail to start completely

Possible Causes:

Defective TPS
Open or short in TPS circuit
Loose or bad connection to TPS
PCM is defective (least likely but not unlikely)

Diagnostic Steps:

Visually inspect all wiring to TPS for loose, open or short connections
Using an OBD2 scanner, check for live and freeze frame data from TPS. If it doesn’t read .5 at idle and 4.5 at full throttle the TPS is faulty

P0122 Throttle/Pedal Position Sensor/Switch A Circuit Low Input

P0122 means that the PCM is reporting that the TPS has recorded a voltage that is lower than the normal minimum limit. The value varies from one car to another but the code may come when the voltage hits .20V or less.

Main Symptoms:

Check Engine Light comes on
Extremely high idle
Rough or low idle
Car stalls
Acceleration is low or completely lacking

Possible Causes:

Defective TPS
Open or short in TPS circuit
Improper mounting of TPS after replacement
TPS has loosened
PCM is defective (least likely but not unlikely)

Diagnostic Steps:

Visually inspect all wiring to TPS for loose, open or short connections
Check that TPS is tightly in position, especially if you recently replaced it

P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

P0128 OBD2 code shows that the PCM has detected that the engine has not attained the required temperature despite being on for enough time to attain that temperature

Main Symptoms:

Check Engine Light MAY come on
Engine temp drops when the vehicle is in high speed
Engine takes abnormally long to warm

Possible Causes:

Most likely cause is that thermostat is leaking or stuck in open position
Engine coolant level is too low
Defective IAT sensor
Defective ECT sensor
Defective cooling fan

Diagnostic Steps:

Check whether coolant strength and level are in the recommended range
Check whether IAT sensor, ECT sensor and coolant fan are working
If all the above are okay then the thermostat is the problem

P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)

P0131 triggers when the ECM has determined that there’s a low voltage condition in bank 1 sensor 1; i.e. O2 sensor voltage remained too low for longer than 2 minutes.

Main Symptoms:

Check Engine Light comes on
Car produces black smoke (visible at tailpipe)
Poor fuel economy
Engine may fail to start completely
If it starts it may run rough and/or stumble

Possible Causes:

Mostly a problem related to corrosion, loose terminal or burnt wire in the O2 sensor 1 connector
Defective O2 sensor
Open or short in wiring to O2 sensor
O2 circuit is experiencing high resistance

Diagnostic Steps:

Visually inspect all wiring to O2 sensor 1 for loose, open or short connections
Use a wiggle test to determine where the voltage drops out
Using an OBD2 scanner, check whether sensor 1 of bank 1 is switching properly

P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)

P0133 occurs when the O2 sensor or ECM can’t adjust air to fuel ratio as it’s supposed to even when the engine is running.

Main Symptoms:

Generally doesn’t come with symptoms. However, in some cases the Check Engine Light may come on and fuel economy may reduce

Possible Causes:

First O2 sensor in bank 1 is faulty
Short, open or broken wire in O2 sensor circuit
Exhaust leak

Diagnostic Steps:

Visually inspect all wiring to first O2 sensor for loose, open or short connections
• Use a wiggle test to determine where the voltage drops out
• Visually check for exhaust leaks or air inlet leaks
• Using an OBD2 scanner, check whether sensor 1 of bank 1 is switching properly

P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

Usually, when O2 heater attains operating temperature, O2 sensor switches based on ambient temp. If ECM determines that the O2 sensor took too long to switch this code is set. It applies to the first sensor of bank 1

Main Symptoms:

Check Engine Light comes on
Poor fuel economy

Possible Causes:

Short, open or broken wire in O2 heating system
High resistance in O2 heater element or circuit

Diagnostic Steps:

Visually inspect all wiring to first O2 sensor (bank 1) for loose, open or short connections
Use a wiggle test to determine where the voltage drops out
If the code is persistent replace O2 sensor

P0136 O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)

P0136 means that the ECM has determined that the there’s a low voltage condition in bank 1 sensor 2; i.e. O2 sensor voltage remained too low for longer than 2 minutes.

Main Symptoms:

Check Engine Light comes on
Car produces black smoke (visible at tailpipe)
Poor fuel economy
Engine may fail to start completely
If it starts it may run rough and/or stumble

Possible Causes:

Mostly a problem related to corrosion, loose terminal or burnt wire in the O2 sensor 2 connector
Defective O2 sensor
Open or short in wiring to O2 sensor
O2 circuit is experiencing high resistance

Diagnostic Steps:

Visually inspect all wiring to O2 sensor 2 for loose, open or short connections
Use a wiggle test to determine where the voltage drops out
Using an OBD2 scanner, check whether sensor 2 of bank 1 is switching properly

P0137 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)

Basically same as P0136. The P0137 is triggered when the PCM has detected that the O2 sensor may be inactive.

Main Symptoms:

Generally doesn’t come with symptoms. However, in some cases the Check Engine Light may come on and fuel economy may reduce

Possible Causes:

Faulty O2 sensor
Short, open or broken wire in O2 sensor circuit
Defective heater circuit in O2 sensor
High resistance in O2 heater element or circuit
Faulty fuel pump regulator resulting in very high or very low fuel pressure
Exhaust leak

Diagnostic Steps:

Visually inspect all wiring to O2 sensor for loose, open or short connections
Use a wiggle test to determine where the voltage drops out
Visually check for exhaust leaks or air inlet leaks
If the code is persistent replace O2 sensor

P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)

The P0138 code means heated O2 sensor in bank 1 sensor 2 is giving a higher voltage reading than it should. For most vehicles the code comes when voltage exceeds 1.5V.

Main Symptoms:

Generally doesn’t come with symptoms. However, in some cases the Check Engine Light may come on and fuel economy may reduce

Possible Causes:

Fuel temp is excessively high
Short, open or broken wire in O2 sensor circuit

Diagnostic Steps:

Visually inspect all wiring to O2 sensor for loose, open or short connections
Use a wiggle test to determine where the voltage drops out
Using an OBD2 scanner, check whether sensor 1 of bank 2 is switching properly

P0141 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

P0141 means when O2 heater attains operating temperature, O2 sensor switches based on ambient temp. If ECM determines that the O2 sensor took too long to switch this code is set. It applies to the second sensor of bank 1.

Main Symptoms:

Check Engine Light comes on
Poor fuel economy

Possible Causes:

Short, open or broken wire in O2 heating system
High resistance in O2 heater element or circuit

Diagnostic Steps:

Visually inspect all wiring to second O2 sensor (bank 1) for loose, open or short connections
Use a wiggle test to determine where the voltage drops out
If the code is persistent replace O2 sensor

P0161 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

P0161 triggers when O2 heater attains operating temperature, O2 sensor switches based on ambient temp. If ECM determines that the O2 sensor took too long to switch this code is set. It applies to the second sensor of bank 2.

Main Symptoms:

Check Engine Light comes on
Poor fuel economy

Possible Causes:

Short, open or broken wire in O2 heating system
High resistance in O2 heater element or circuit

Diagnostic Steps:

Visually inspect all wiring to second O2 sensor (bank 2) for loose, open or short connections
Use a wiggle test to determine where the voltage drops out
If the code is persistent replace O2 sensor

P0171 System Too Lean (Bank 1)

P0171 indicates that there is a lean condition in bank 1; i.e. there’s excess oxygen in the exhaust

Main Symptoms:

Significant decrease in engine power
Car hesitates then surges upon acceleration
Rough idle

Possible Causes:

Dirty or defective MAF sensor
MAF sensor has a vacuum leak
Positive Crankcase Ventilation (PCV) valve is stuck in open position
Leak either in PCV or vacuum system

Diagnostic Steps:

Inspect MAF sensor in bank 1 for dirt and debris
Check whether fuel pressure is correct
Check vacuum and PCV for leaks
Run a smog test using OBD2 scanner

P0172 System Too Rich (Bank 1)

P0172 happens when there’s a rich condition in bank 1; i.e. there’s too little oxygen in the exhaust condition in bank 1; i.e. there’s excess oxygen in the exhaust.

Main Symptoms:

Generally doesn’t come with symptoms but the Check Engine Light may come on and engine may misfire

Possible Causes:

Dirty or defective MAF sensor
MAF sensor has a vacuum leak
Problem relating to fuel pressure or delivery

Diagnostic Steps:

Inspect MAF sensor in bank 1 for dirt and debris
Check whether fuel pressure is correct
Inspect fuel lines and injectors for any leaks/openings and dirt
Check vacuum, PCV and exhaust for leaks
Run a smog test using OBD2 scanner

P0174 System Too Lean (Bank 2)

This code means that there’s a lean condition in bank 2; i.e. there’s excess oxygen in the exhaust

Main Symptoms:

Significant decrease in engine power
Car hesitates then surges upon acceleration
Rough idle

Possible Causes:

Dirty or defective MAF sensor
MAF sensor has a vacuum leak
Positive Crankcase Ventilation (PCV) valve is stuck in open position
Leak either in PCV or vacuum system

Diagnostic Steps:

Inspect MAF sensor in bank 2 for dirt and debris
Check whether fuel pressure is correct
Check vacuum and PCV for leaks
Run a smog test using OBD2 scanner

P0300 Random/Multiple Cylinder Misfire Detected

When the code P0300 is triggered, it means that PCM has detected that there’s an engine cylinder that’s not firing properly. It could be one or more cylinders. PCM hasn’t specified the exact cylinder

Main Symptoms:

Check Engine Light comes on
Check Engine Light may flash
Engine lacks power
Engine may be hard to start
Engine may stumble and hesitate frequently

Possible Causes:

Defective or worn out spark plugs
Low fuel pressure
Vacuum leak
Defective catalytic converter
Defective fuel injector
Defective coil
Defective camshaft position sensor
Defective crankshaft sensor
Problem with distributor

Diagnostic Steps:

Using a scan tool, pull codes and see if there are any other besides P0300. Address the others first
Inspect whether there are loose, open or short wires in ignition coils
Inspect whether spark plugs and their wires are in good condition
Check that fuel pressure is within the recommended range
Inspect fuel injectors to see whether they are in good condition

P0301 Cylinder 1 Misfire Detected

The meaning of P0301 is that the PCM has detected that cylinder #1 is not firing properly.

Main Symptoms:

Check Engine Light comes on
Check Engine Light may flash
Engine lacks power
Engine may be hard to start
Engine may stumble and hesitate frequently

Possible Causes:

Defective or worn out spark plugs in cylinder 1
Low fuel pressure
Vacuum leak
Defective catalytic converter
Defective fuel injector
Defective coil
Defective camshaft position sensor
Defective crankshaft sensor
Problem with distributor

Diagnostic Steps:

Using a scan tool, pull codes and see if there are any other besides P0301. Address the others first
Inspect whether there are loose, open or short wires in ignition coils in cylinder 1
Inspect whether cylinder 1 spark plugs and their wires are in good condition
Check that fuel pressure is within the recommended range
Inspect fuel injectors to see whether they are in good condition

P0302 Cylinder 2 Misfire Detected

P0302 indicates that the PCM has detected that cylinder #2 is not firing properly

Main Symptoms:

Check Engine Light comes on
Check Engine Light may flash
Engine lacks power
Engine may be hard to start
Engine may stumble and hesitate frequently

Possible Causes:

Defective or worn out spark plugs in cylinder 2
Low fuel pressure
Vacuum leak
Defective catalytic converter
Defective fuel injector
Defective coil
Defective camshaft position sensor
Defective crankshaft sensor
Problem with distributor

Diagnostic Steps:

Using a scan tool, pull codes and see if there are any other besides P0302. Address the others first
Inspect whether there are loose, open or short wires in ignition coils in cylinder 2
Inspect whether cylinder 2 spark plugs and their wires are in good condition
Check that fuel pressure is within the recommended range
Inspect fuel injectors to see whether they are in good condition

P0303 Cylinder 3 Misfire Detected

The P0303 code occurs when the PCM has detected that cylinder #3 is not firing properly.

Main Symptoms:

Check Engine Light comes on
Check Engine Light may flash
Engine lacks power
Engine may be hard to start
Engine may stumble and hesitate frequently

Possible Causes:

Defective or worn out spark plugs in cylinder 3
Low fuel pressure
Vacuum leak
Defective catalytic converter
Defective fuel injector
Defective coil
Defective camshaft position sensor
Defective crankshaft sensor
Problem with distributor

Diagnostic Steps:

Using a scan tool, pull codes and see if there are any other besides P0303. Address the others first
Inspect whether there are loose, open or short wires in ignition coils in cylinder 3
Inspect whether cylinder 3 spark plugs and their wires are in good condition
Check that fuel pressure is within the recommended range
Inspect fuel injectors to see whether they are in good condition

P0304 Cylinder 4 Misfire Detected

The P0304 code is triggered when the PCM has detected that cylinder #4 is not firing properly.

Main Symptoms:

Check Engine Light comes on
Check Engine Light may flash
Engine lacks power
Engine may be hard to start
Engine may stumble and hesitate frequently

Possible Causes:

Defective or worn out spark plugs in cylinder 4
Low fuel pressure
Vacuum leak
Defective catalytic converter
Defective fuel injector
Defective coil
Defective camshaft position sensor
Defective crankshaft sensor
Problem with distributor

Diagnostic Steps:

Using a scan tool, pull codes and see if there are any other besides P0304. Address the others first
Inspect whether there are loose, open or short wires in ignition coils in cylinder 4
Inspect whether cylinder 4 spark plugs and their wires are in good condition
Check that fuel pressure is within the recommended range
Inspect fuel injectors to see whether they are in good condition

P0305 Cylinder 5 Misfire Detected

The P0305 code indicates that the PCM has detected that cylinder #5 is not firing properly.

Main Symptoms:

Check Engine Light comes on
Check Engine Light may flash
Engine lacks power
Engine may be hard to start
Engine may stumble and hesitate frequently

Possible Causes:

Defective or worn out spark plugs in cylinder 5
Low fuel pressure
Vacuum leak
Defective catalytic converter
Defective fuel injector
Defective coil
Defective camshaft position sensor
Defective crankshaft sensor
Problem with distributor

Diagnostic Steps:

Using a scan tool, pull codes and see if there are any other besides P0305. Address the others first
Inspect whether there are loose, open or short wires in ignition coils in cylinder 5
Inspect whether cylinder 5 spark plugs and their wires are in good condition
Check that fuel pressure is within the recommended range
Inspect fuel injectors to see whether they are in good condition

P0306 Cylinder 6 Misfire Detected

The P0306 code is triggered when the PCM has detected that cylinder #6 is not firing properly.

Main Symptoms:

Check Engine Light comes on
Check Engine Light may flash
Engine lacks power
Engine may be hard to start
Engine may stumble and hesitate frequently

Possible Causes:

Defective or worn out spark plugs in cylinder 6
Low fuel pressure
Vacuum leak
Defective catalytic converter
Defective fuel injector
Defective coil
Defective camshaft position sensor
Defective crankshaft sensor
Problem with distributor

Diagnostic Steps:

Using a scan tool, pull codes and see if there are any other besides P0306. Address the others first
Inspect whether there are loose, open or short wires in ignition coils in cylinder 6
Inspect whether cylinder 6 spark plugs and their wires are in good condition
Check that fuel pressure is within the recommended range
Inspect fuel injectors to see whether they are in good condition

P0316 Misfire Detected On Startup (First 1000 Revolutions)

The P0316 code occurs when the PCM has detected a misfire less than 1,000 revolutions after startup.

Main Symptoms:

Check Engine Light comes on
Engine lacks power
Rough idle

Possible Causes:

Defective or worn out spark plugs
No fuel
Low fuel pressure
Vacuum leak
Defective catalytic converter
Defective fuel injector
Defective coil
Defective crankshaft sensor
Wiring fault in crankshaft position sensor
Problem with PCM

Diagnostic Steps:

Pull all codes then address other misfire codes first
Check all wiring and connectors in crankshaft and camshaft position sensors
Review freeze frame data to narrow down the problem further

P0325 Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)

The P0325 code is triggered when the PCM has detected that the engine’s knock sensor 1 in circuit bank 1 is not working properly.

Main Symptoms:

Generally doesn’t come with symptoms but Check Engine Light may come on.
Engine may also lose power

Possible Causes:

First sensor in circuit bank 1 may be faulty
Open or short in wiring to the sensor
Problem with engine coolant
Engine is excessively lean
PCM has failed (least likely)

Diagnostic Steps:

Visually inspect all wiring to knock sensor 1 in circuit bank 1. Ensure there are no shorts or open wires
View coolant temp data to check for issues
If there are none, clear the code and test drive the car. If it comes back the sensor is defective

P0335 Crankshaft Position Sensor A Circuit Malfunction

The P0335 code happens when the PCM has detected that crankshaft position (CKP) sensor is not producing pulses or the pulses are not normal. It uses these pulses to determine the position of the crankshaft.

Main Symptoms:

Check Engine Light comes on
Engine may fail to start
Vehicle may run rough

Possible Causes:

Defective CKP sensor
Open or short in CKP sensor wiring
Timing belt is broken
PCM has failed (least likely)

Diagnostic Steps:

Start by checking if there’s an RPM signal (using a scanner)
If it’s not there check all the wires and connectors to the sensor. Repair as necessary
Check the sensor’s resistance and compare with manufacturer’s recommendation. If they don’t match replace sensor

P0340 Camshaft Position Sensor Circuit Malfunction

This OBD2 code means that there’s a problem with the camshaft position sensor (CPS) circuit. As such, PCM can’t perform ignition spark and fuel injector timing properly

Main Symptoms:

Check Engine Light comes on
Engine may fail to start
Vehicle may run rough
Rough idle
Misfire

Possible Causes:

Defective CPS
Open or short in CPS wiring
Defective CKP sensor
PCM has failed (least likely)

Diagnostic Steps:

Inspect wiring to CPS and ensure there are no open or broken wires
Check CPS voltage if it’s within the manufacturer’s specs. If it’s not replace sensor
Check CKP sensor as well to determine whether it’s the source of the problem

P0401 Exhaust Gas Recirculation Flow Insufficient Detected

This code indicates that the PCM has detected an insufficient amount of EGR.

Main Symptoms: Most notable symptom is engine pinging when the vehicle is in high speed or under load

Possible Causes:

Defective differential pressure feedback EGR (DPFE) sensor
Defective EGR valve
EGR valve can’t open because of lack of vacuum
Blockage in EGR tube

Diagnostic Steps:

Check EGR valve and its tubing for deposits
Check DPFE sensor voltage to ensure its within specified range
If not replace the sensor. If it is replace the EGR valve

P0420 Catalyst System Efficiency Below Threshold (Bank 1)

P0420 means the Catalytic converter is not working as efficiently as it should and the vehicle is therefore emitting more harmful substances.

Main symptoms:

Check Engine Light comes on
Engine lacks power
Reduced fuel economy

Possible Causes:

Defective O2 sensor
Defective engine coolant temp
Wiring to downstream O2 sensor is damaged or improperly done
Leaking fuel injector
Oil is contaminated
Using leaded fuel where unleaded fuel was required
Defective catalytic converter, exhaust pipe, muffler or exhaust manifold

Diagnostic Steps:

Inspect exhaust system for damage and leaks.
Check voltage of downstream O2 sensor while the engine is running. If its not steady (jumpy between .1 and .9 V) then the catalytic converter needs replacing

P0440 Evaporative Emission Control System Malfunction

The code P0440 means a component in the EVAP system is not working properly

Main Symptoms: Check Engine Light may come on

Possible Causes:

Gas cap is not working or has not been installed properly
Canister is plugged and defective
Purge solenoid has failed

Diagnostic Steps:

Inspect gas cap to see if its installed tightly
Check for disconnected or cracked EVAP hoses
Inspect charcoal canister and fuel tank for leaks and damages
Check that purge valve (solenoid) has no leaks

P0441 Evaporative Emission Control System Incorrect Purge flow

P0441 code is triggered when the PCM finds that there’s no purge flow (i.e. purge control valve is still closed) despite commanding a purge

Main Symptoms:

Check Engine Light may come on
Rough or erratic idle

4. Possible Causes:

Loose or damaged EVAP hoses
Defective purge valve
Gas cap is loose, missing or damaged
Charcoal canister is damaged or defective

5. Diagnostic Steps:

Inspect gas cap to see if its installed tightly
Check for disconnected or cracked EVAP hoses
Inspect charcoal canister and fuel tank for leaks and damages
Check that purge valve (solenoid) has no leaks

P0442 Evaporative Emission Control System Leak Detected (small leak)

The code P0442 indicates that the PCM has detected a very small vapor leak somewhere in the EVAP control system

Main Symptoms:

Check Engine Light may come on
Reduced fuel economy

Possible Causes:

Loose or damaged EVAP hoses
Defective purge valve
Gas cap is loose, missing or damaged
Charcoal canister is leaking
Fuel tank is leaking

Diagnostic Steps:

Inspect gas cap to see if its installed tightly
Check for disconnected or cracked EVAP hoses
Inspect charcoal canister and fuel tank for leaks and damages
Check that purge valve (solenoid) has no leaks
If the above don’t narrow down the problem perform a smoke test

P0443 Evaporative Emission Control System Purge Control Valve circuit Malfunction

This code means that either there’s an open in the purge control valve circuit or the circuit has abnormal voltage (too high or too low)

Main Symptoms:

Check Engine Light may come on
Car may have lean condition

Possible Causes:

Purge solenoid has short or open
Short or open somewhere in the wiring harness to purge valve
Driver circuit in PCM has an open or short
Water intrusion has caused connector to break or wear out

Diagnostic Steps:

Using a scan tool, command purge valve to open. Listen for a clicking sound (one or many times)
If it doesn’t click examine solenoid and connectors for breakages and signs of extreme wearing out
Check all the circuits for wiring problems

P0446 Evaporative Emission Control System Vent Control Circuit Malfunction

The P0446 indicates that the PCM has detected an open or short in EVAP control circuit or a short to ground circuit

Main Symptoms:

Check Engine Light comes on

Possible Causes:

Defective EVAP vent valve
Blockage in vent valve
Vent valve control circuit has an open or short

Diagnostic Steps:

Examine all wiring to vent valve
If the above checks out replace vent valve

P0449 Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction

This code happens when the PCM has detected a problem in the circuit that controls the EVAP system vent.

Main Symptoms:

Check Engine Light comes on

Possible Causes:

Defective EVAP vent valve
Wiring issue in the EVAP vent valve
Circuit issue in the EVAP vent valve

Diagnostic Steps:

Check all wires leading to the vent valve for shorts and opens
Check fuses that power the vent solenoid (in case there are any)
Examine if vent valve has cracks or openings
Using a bidirectional scanner, actuate the valve to see if its working

P0452 Evaporative Emission System Pressure Sensor/Switch Low

The P0452 code indicates that the PCM has detected that the fuel tank pressure is abnormally low.

Main Symptoms:

Check Engine Light comes on

Possible Causes:

Defective fuel tank pressure (FTP) sensor
Wiring problem in the circuits that lead to FTP sensor
Broken or cracked vapor line (either to the tank or vacuum canister)
Loose gas cap leading to loss of vacuum
Leaking gasket in fuel pump module

Diagnostic Steps:

Check vapor hoses for any breakages and opens
Since diagnosing this problem is extremely hard (due to the location of the FTP sensor), its recommended that you get a professional to do the job

P0455 Evaporative Emission Control System Leak Detected (large leak)

P0455 code means that PCM has detected a large vapor leak somewhere in the EVAP control system

Main Symptoms:

Check Engine Light may come on
Reduced fuel economy

Possible Causes:

Loose or damaged EVAP hoses
Gas cap is loose, missing or damaged
Non-compatible gas cap

Diagnostic Steps:

Inspect gas cap to see if its installed tightly
Check for disconnected or cracked EVAP hoses
Inspect charcoal canister and fuel tank for leaks and damages
If the above don’t work replace the gas cap

P0456 Evaporative Emissions System – Small leak detected

P0456 code means the FTP sensor has detected a small leak in EVAP system.

Main Symptoms: Check Engine Light comes on

Possible Causes:

Faulty gas cap
Leak in fuel tank hoses or EVAP hoses
Leak in vent valve or purge valve
Leak in EVAP canister

Diagnostic Steps:

Use a bidirectional tool to activate vent solenoid as you monitor FTP sensor. It will tell you if the system is sealing properly or not
If it is then use a smoke test to determine the leak

P0457 Evaporative Emission Control System (EVAP) Leak Detected

When there’s a vacuum leak and the EVAP system can’t draw fuel vapors into the system for efficient burning, the P0457 is triggered.

Main Symptoms:

Check Engine Light comes on
Smell of fuel in exhaust
Reduced fuel economy

Possible Causes:

Check Engine Light comes on
Smell of fuel in exhaust
Reduced fuel economy

Diagnostic Steps:

Inspect gas cap and check if its loose or has debris that’s preventing it from fitting tightly
Inspect vacuum hoses for cracks and breaks
Inspect charcoal canister for leaks

P0463 Evaporative Emission Control System Pressure Sensor High Input

When the signal from the fuel level sensor is above 5 volts for a prolonged period of time, P0463 happens.

Main Symptoms:

Check Engine Light comes on
Fuel light may come on and sound alarm
Fluctuating fuel level gauge
Fuel level gauge may erroneously read empty or full

Possible Causes:

Defective fuel level sensor
Problem with fuel level sensor circuit
Defective instrument cluster
Damaged fuel tank

Diagnostic Steps:

Visually inspect fuel tank for damage or leaks
Inspect wiring harness
Do voltage test on fuel level sensor circuit
If all those check out you may have to replace fuel tank

P0507 Idle Control System RPM higher Than Expected

The PCM has detected that the engine idle speed is higher than the pre-programmed RPM (typically over 200 RPM)

Main Symptoms:

Check Engine Light comes on

Possible Causes:

Vacuum leak
Defective positive crankcase ventilation valve
Leaking air intake
Problem with throttle body
Defective EVAP system
Defective idle air controller (IAC) or a problem with IAC circuit
Failed PCM

Diagnostic Steps:

Check for vacuum leaks, damages and restriction
Note that this code is informational more than anything, so look out for other codes that it comes with and address those first

P0700 Transmission Control System Malfunction

If the transmission control module (TCM) detects a fault in the transmission system and sets a code, this code will be triggered.

Main Symptoms:

Check Engine Light comes on
Transmission may exhibit problems

Possible Causes: Any transmission-related problem can trigger this code

Diagnostic Steps: This is only an informational code, so pull all transmission codes, address them and do a test drive to fix this code

Still cannot find your code? Search below!!

Car Diagnostic Codes FULL List: Search Your Codes HERE

Powertrain (P) OBDII Codes Fixes

TIP: Use the “Search Box” to find the meaning and fix guide for your code.

OBD2 Codes	Meaning & Fix Guide
P0008	P0008 - Engine Position System Performance
P0010	P0010 - "A" Camshaft Position Actuator Circuit/Open
P0011	P0011 - "A" Camshaft Position - Timing Over-Advanced or System
P0012	P0012 - "A" Camshaft Position - Timing Over-Retarded
P0013	P0013 - “B” Camshaft Position Actuator Circuit (Bank 1)

Network (U) OBD-II Codes Fixes

TIP: Use the “Search Box” to find the meaning and fix guide for your code.

OBD2 Codes	Meaning & Fix Guide
U0001	U0001 - High Speed CAN Communication Bus
U0073	U0073 – Control Module Communication Bus “A” Off
U0101	U0101 – Lost Communication With Transmission Control Module
U0107	U0107 – Lost Communication With Throttle Actuator Control Module
U0121	U0121 – Lost Communication With Anti-Lock Brake System Control Module

Body (B) OBD2 Codes Fixes

TIP: Use the “Search Box” to find the meaning and fix guide for your code.

OBD2 Codes	Meaning & Fix Guide
B0092	B0092 – Left Side Restraints Sensor 2
B1047	B1047 – Driver-Side Side Air Bag Module And Other Air Bag Module Circuits Short
B1057	B1057 – Driver Airbag Module Short
B1318	B1057 – Driver Airbag Module Short
B1342	B1342 – ECU Is Defective

Chassis (C) OBD II Codes Fixes

TIP: Use the “Search Box” to find the meaning and fix guide for your code.

OBD2 Codes	Meaning & Fix Guide
C0265	C0265 – EBCM Motor Relay Circuit Low When On
C1130	C1130 – Engine Signal 1
C1145	C1145 – Right Front Wheel Speed Sensor Input Circuit Failure
C1201	C1201 – Engine Control System Malfunction
C1223	C1223 – ABS Control System Malfunction

C1233	C1233 – Left Front Wheel Speed Sensor Input Signal Missing
C1234	C1234 – Right Front Wheel Speed Sensor Input Signal Missing
C1241	C1241 – Low Battery Positive Voltage
C1713	C1713 – Right Rear Height Control Sensor Circuit

OBD-II Mega list

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OBD2 Codes List for FREE Download

Generic Powertrain OBD2 Trouble Codes

Generic Chassis, Network, and Body Codes

Manufacturer-Specific Codes

OBD2 Codes: Meaning, Causes, and Fixes

Car Diagnostic Codes FULL List: Search Your Codes HERE

Powertrain (P) OBDII Codes Fixes

Network (U) OBD-II Codes Fixes

Body (B) OBD2 Codes Fixes

Chassis (C) OBD II Codes Fixes

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