Overview of the Most Common OBD2 Codes [2020]

Cars are extremely important in your day-to-day functioning, but like most other things in our possession, they can undergo certain problems, too.

In such cases, diagnostic trouble codes help in the timely identification of these problems so you can fix them and return to your fast-paced life instantly.

To make it easy to identify problems, here’s the list of the most common OBD2 codes.

What Are OBD2 Codes?

OBD2 codes, or diagnostic trouble codes, as they are generally known, are trouble codes designed specifically for your car. They are used in accordance with the OBD system of your car to help notify you about any issue with your car.

Your car stores all these trouble codes in its memory and whenever a problem occurs within your car, these codes notify you about the ongoing issue. There are thousands of codes available and each one consists of one letter and four digits. Understanding these codes can be a nuisance. Hence, this article will not only help you in interpreting these codes, but will also help you learn about the most effective codes.

Understanding Data Trouble Codes

Since these codes are many in number, it often becomes hard for consumers to understand their meaning, but it’s actually not that difficult. OBD2 codes are categorized into four different systems, each represented by a unique letter. Here is what each letter stands for.

P Codes

These are referred to as the powertrain category and covers functions including the engine and transmission. Not just that, P codes also help identify the issues in the associated drivetrain accessories.

C Codes

This refers to the chassis category. These OBD2 codes deal with functions that are outside of the passenger’s compartments. These include most of the mechanical systems in your car, like the steering, brakes, and suspension.

B Codes

This deals with the body category issues. They are sometimes considered less important than the three other codes, mainly because they deal with functions inside the passenger’s compartment. They assist and are provided for the driver’s safety, comfort, and convenience.

U Codes

Lastly, we have the U codes that deal with network and vehicle integration inside the car. These codes cover functions that are generally shared between various systems and computers on the vehicle. They are important, as they ensure that all functions of your car are in accordance with each other.

List of P Codes

The P refers to all the problems in the powertrain of the car. The P codes deal with functions and issues in the engines and transmission of the car. The 0 here means that it’s a generic code while the 2 here refers to the fuel-air mattering or the injector circuit system. Lastly, the two digits define the problem. For instance, if the last two digits are 19, then this hints at an over-speed condition.

1. P0008

The code is used for engine position system performance. It notifies that the engine control module of the car is experiencing timing issues. It also indicates that there is a difference in the mechanical timing of bank one's camshaft and crankshaft.

Main Symptoms

  • Rough acceleration
  • A decrease in the car’s overall power
  • Fuel economy lowered
  • Appearance of the check engine light

Causes

  • Tension in timing chain
  • Stretched time chain
  • Damage in the wiring
  • Timing components have worn down
  • ECM has undergone internal damage

Diagnostic Steps That You Can Take

You can visually inspect the VCT or the VVT circuit for any open or damaged wires. Alternatively, you can use an advanced tool to pull out any engine codes.

2. P0011

The P0011 is another very important P-code that helps identify the intake camshaft position timing and is related to the over advanced bank one. It means that the timing for the bank one is beyond or above the standard limit set by the ECM.

Main Symptoms

  • Stalling or rough running of the card
  • Hard starting occurs
  • Car tends to fail the emission test
  • Poor idle
  • Check engine light will come on
  • Fuel economy becomes poor

Causes

  • Clogged or stuck bank 1 oil control solenoid
  • Wiring problems in VVT or VCT
  • VCT piston chamber will experience an overflow of oil
  • Passage in bank 1 is blocked by the thick oil

Diagnostic Steps That You Can ​Take

Check the viscosity of the engine oil and see whether it’s clean. You can also inspect the wiring in the CVT system.

3. P0016

The code is related to the crankshaft position and the camshaft position in correlation to the bank one sensor. This means that the crankshaft signals are out of time. The ECM can detect that the timings of the crankshaft and camshaft don’t correlate with each other.

Main Symptoms

  • Fuel economy is poor
  • Harmonic balancer produces a rattling sound
  • Engine may continue to run but still undergoes poor performance
  • Engine may fail to start entirely

Causes

  • Wiring is cranked or damaged
  • Putting the phaser out of its position
  • Timing chain has jumped teeth and the camshaft is out of position
  • Timing chain is slightly overstretched

Diagnostic Steps That You Can Take

You should first inspect the oil control valve and look for any connections or wiring problems. You should then check whether the engine oil is clean, full, and has the correct viscosity. Lastly, pull the engine codes and live data by using the advanced diagnostic tool.

4. P0134

This code is used for the bank one sensor and indicates when there is no sensor circuit detected. In other words, this means that the PCM has found out that the O2 sensor in bank one is either inactive or open and that it has not warmed up adequately even after one-minute of the engine running.

Main Symptoms

  • Fuel economy is poor
  • Check engine light has come on
  • Black smoke is visible at the tailpipe
  • Stumbling in the car’s engine

Causes

  • O2 sensor is experiencing problems
  • Broken or short wire in the sensor circuit
  • Exhaust leak
  • The PCM is defective
  • Fused heater circuit

Diagnostic Steps That You Can Take

You can inspect the wiring visually in order to identify any short or open connections. Moreover, you can also use a wiggle test to determine where the voltage drops out in the car.

5. P0174

The code is used when the system inside bank two is too lean. Roughly this translates into a serious condition where there is excess oxygen in the exhaust.

Main Symptoms

  • Engine power is decreased
  • Car hesitates while running
  • It gradually surges upon acceleration
  • Rough idle is experienced

Causes

  • MAF sensor is either dirty or defective
  • There is a vacuum leak in the MAF sensor
  • Leak in the PCV
  • Positive crankcase ventilation valve is stuck in open position

Diagnostic Steps That You Can Take

You can inspect the MAF sensor in the bank for either dirt or debris. You can also check whether the pressure of the fuel is correct. Checking for leaks also helps with diagnosis.

List of B Codes

These are a list of essential codes that deal with the body category issues inside the car. The list includes all the codes used to identify issues in the passenger’s compartment. Contrary to what a lot of people think, these codes not only ensure the convenience and comfort of the driver, but they also ensure the driver’s safety.

1. B1342

The code is displayed when the ECU system is defective, meaning that the electronic control unit inside your car has failed.

Main Symptoms

  • The check engine light will come on
  • Other warning lights also come on, but this largely depends upon which module inside your car is affected

Causes

  • Your ESU is defective
  • The abnormality in system voltages have caused a damaged controller

Diagnostic Steps That You Can Take

Replacing ECU immediately is a mistake a lot of people make when dealing with this situation. You should first address any and all codes before replacing ECU. Another way to diagnose is to inspect the wiring of the ECU. Then reset all the codes and do a test drive.

2. B1676

This code is for when your battery pack voltage is out of range. This means the ABS module detects a lower voltage signal for more than eight seconds. The voltage can reduce from 19 V to 9 V.

Main Symptoms

  • Check engine light will come on
  • The ABS warning lights inside the system will come on too

Causes

  • There is a blown fuse in the ABS
  • Defect in ABS module
  • There is a problem in the charging system
  • Wiring problem in the ABS module connector

Diagnostic Steps That You Can Take

Firstly, you should inspect the wiring and connectors in your ABS module and then charge the system for any loose, open, or short connections. Testing the resistance of the ABS module with the manufacture’s specs also helps with diagnosis.

3. B1650

This code deals with faults in the occupation classification system. This indicates that the PCM or the airbag control module has detected a malfunction in the occupant classification system of your car.

Main Symptoms

  • Check engine light comes on
  • Airbag warning light comes on

Causes

  • There is a problem in the airbag sensor assembly center
  • Wiring problem in the right front seat
  • Possible problem in the occupation classification system

Diagnostic Steps That You Can Take

First, inspect the wiring in your occupation classification system and see if there are any short or open connections. You can also perform a resistance test on the system to see if replacements are required.

4. B1676

This code helps identify issues in the battery pack voltage. The anti-lock brake system is set when the ABS model detects a voltage signal that is less than 19V. To fit the criteria, this reduction should go on for at least eight seconds.

Main Symptoms

  • Check engine light comes on
  • ABS warning light also comes on

Causes

  • A defective ABS module
  • There is a wiring problem in the ABS module connector
  • Charging system has problems
  • ABS has a blown fuse

Diagnostic Steps That I Can Take

Reset codes and do test drives. If the code returns, only then think of replacing the module. You can also check to see whether all wiring and connectors in the ABS module are working adequately. You can also check for fuses in the system.

5. B1047

This is for the driver side airbag module and the other airbag module circuits. The code is activated when there is a short in the side airbag on the driver’s side.

Main Symptoms

  • There is abnormal illumination of airbag warning lights
  • The airbag warning lights also come on

Causes

  • There is a defect in the SRS airbag module
  • There is a defect in the driver side safe airbag module
  • Short or open in the circuit leading to driver side airbag module

Diagnostic Steps That You Can Take

Firstly, check all the wiring to the driver side airbag and see whether there are any open, loose, or short connections. You can also perform a resistance test on the airbag module. Lastly, perform a resistance test on the airbag control module.

List of C Codes

C codes refer to the chassis category and their main purpose is to deal with and identify problems outside the passenger’s compartments. These mostly include mechanical systems like the brakes and the suspension. The digits 0 and 1 in these codes refer to a generic or a manufacturing category.

1. C1130

This C code is for engine signals. Since the engine is practically the most important part of your car, this C code is considered to be one of the most vital ones. It is activated when there is a possible problem in either the engine control unit or the PCM of your car.

Main Symptoms

  • Check engine light turns on
  • ABS warning lights come on too

Causes

  • Abnormal system voltages cause a damaged controller
  • The communication line has a problem
  • A defect in ECU
  • Defect in ABS actuator
  • Defect in ABS control module

Diagnostic Steps That You Can Take

Before replacing the ECU, diagnose and address all the additional problems in the car. You can check whether the system voltage of your car is within the manufacturer’s recommendations. Another option could be to check for all the fuses and see if a replacement is required.

2. C1201

The code deals with any malfunctions in the engine control system and helps identify if and when the electronic control unit or the ECU has undergone a failure.

Main Symptoms

  • Warning lights are turned on depending upon the type of module that is affected
  • The check engine light comes on

Causes

  • Abnormality in the system voltages lead to a damaged controller
  • There is a defect in the ECU

Diagnostic Steps That You Can Take

Before replacing any systems, make sure that you do a proper diagnosis and then address the codes that are activated. You should also check whether the system is consistent with the manufacture’s recommendations.

3. C1223

This C code is for the ABS control system malfunction. This particular code is set in the car’s VSC, or the vehicle stability system. It helps in the identification of the malfunction in ABS.

Main Symptoms

  • Check engine light comes on
  • ABS warning light also comes on immediately

Causes

  • Defect in ABS control module
  • Defect in ABS sensor
  • Short or open in the ABS circuit

Diagnostic Steps That You Can Take

The first step is to visually check the wiring in your ABS circuit and look for any open, loose, and short connections. Then you should perform a resistance test on ABS sensors and modules. Only replace the system if all other options fail. You can also reset the codes and go for a test drive.

4. C1233

The C1233 is one of the most important codes that deal with left front wheel speed sensors. The PCM, or the Vehicle Speed Sensor (VSS) deals with missing signals and helps identify when the signals have not been received from the left front wheel sensors. Other codes in this category deal with the remaining three tires and are equally important.

Main Symptoms

  • Check engine light comes on
  • ABS warning light comes on too

Causes

  • There is a defect in the left front wheel speed sensor
  • Left front wheel speed sensor is dealing with an open, short, or broken wire
  • There is a poor connection in the left front wheel speed sensor

Diagnostic Steps That You Can Take

Firstly, visually check all the wiring in the left front wheel speed sensor and look for any loose or open connections. Performing a resistance test on the sensor is also a good option and it will tell you whether replacement is necessary. Lastly, reset the codes and do a drive cycle.

5. C1241

The code is for low battery positive voltage. It is set when there is a problem with the skid control ECU, which is also known as the master cylinder solenoid.

Main Symptoms

  • Check engine light comes on
  • ABS warning light comes on

Causes

  • Use of an incorrect battery
  • Battery voltage is lower than required
  • Defective charging system
  • High resistance in the alternator battery circuit
  • The battery is not maintained properly

Diagnostic Steps That You Can ​Take

Check whether the battery voltage is sufficient. Once you have ruled that out as a probable reason, then ensure that the battery is properly connected to the alternator belt. Lastly, reset the code, and then do a test drive.

List of U Codes

Last but not least, U codes in the OBD2 system deal with network issues. They also help to identify problems with in-vehicle integration inside the car. The codes are important as they ensure that relations and communication between all systems are smooth. Moreover, it also helps to ensure that the shared functions of the various systems are not hindered.

1. U0001

This is one of the most frequent U codes. It is related to the controller area network and high-speed bus communication control module. There is a line between the car’s TIPM and other vehicle modules. The setting of this code indicates that the ABS module has failed in its communication with TIPM.

Main Symptoms

  • Vehicle doesn’t start on one or even several attempts
  • The check engine light immediately comes on
  • The key alarm activates

Causes

  • The CAN bus circuit experiences a positive or negative
  • Short to ground on CAN bus circuit
  • Problem in the TIPM system
  • Low voltage in the car

Diagnostic Steps That You Can Take

 You can use an OBD2 scanner to operate on each module separately. This will inform you about the exact part that is not working. You can also use an ohmmeter to check continuity in wire terminals.

2. U1021

This code is used when you have lost communication with the anti-lock brake system in the control module. This means that there is no communication between ABS and any other control module

Main Symptoms

  • The ABS warning light will come on
  • The TRAC or the ESC’s lights will appear
  • The check engine light will come on

Causes

  • Defect in ABS control module
  • The CAN bus will experience a positive or negative OPEN reaction
  • There is a shortage of power in the CAN circuit

Diagnostic Steps That You Can Take

You can use the BDS scanner to see whether or not the ABS control module responds. If it doesn’t, you can probe it further. In case it responds, you need to then check for faulty wires inside the car. You can also check the voltage of the CAN to match it with the expected voltage.

3. U1318

This code is used when the battery voltage is significantly low. It is used when the PCM detects that the battery has fallen low and is lower than the predetermined level.

Main Symptoms

  • Red battery light comes on
  • Transmission may fall
  • Failure to start the engine
  • The fuel economy will be lowered
  • Check engine light will come on

Causes

  • Use of an incorrect battery
  • Battery has not been properly maintained
  • Defect in the alternator
  • There is high resistance in the alternator circuit, PCM, or both

Diagnostic Steps That You Can Take

You should check whether the battery voltage is sufficient and also ensure that the battery is properly connected with the alternator belt. Using a digital ohmmeter will also help in the diagnosis.

4. U0073

The code is made for control module communication. It helps to identify the problems with CAN bus. These could include issues that make it hard for the module to communicate or exchange information with the scan tool

Main Symptoms

  • The instrument cluster indicator light comes on
  • Check engine light will appear
  • Fuel economy is lowered
  • Engine will lack power

Causes

  • Shortage in power or ground in A CAN bus circuit
  • The A CAN bus circuit has a positive or negative OPEN defect

Diagnostic steps that you can take

Firstly, pull other communication codes and only then address this issue. You can also inspect all the bus communication connections and then reset all codes to do a test drive.

5. U1055

This is perhaps the most important U code. It deals with the panel control module. It helps identify when there is no communication between the instrument panel control (IPC) module and the various other modules in the car.

Main Symptoms

  • All indicator lights in the instrument panel will come on
  • Check engine light will come on
  • All indicator lights in the cluster will come on

Causes

  • There is a positive or negative OPEN effect on the CAN bus
  • Short to power in the ground in either positive or negative CAN bus circuit
  • Defect in the IPC module

Diagnostic steps that you can take

You can use a BDC scan tool to control the IPC module, and if it doesn’t respond, try probing into the problem further. In case it does respond, you can check all the wires, fuses, and connectors in the circuit.

Conclusion

Cars are complex machines, and their maintenance can become very hard without proper tools. OBD2 codes are essential in assuring the timely recognition of the issues and problems in your cars. Once you understand the problem, you can easily fix it either manually or through the help of an expert. The most common codes are mentioned in this article so that when you encounter them, you know exactly what you have to do.

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