Fault code P2BAC – NOx exceedence – deactivation of EGR

Fault code P2BAC is called “NOx Exceedence – Deactivation of EGR” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P2BAC

The OBD-II P2BAC error code is a general fault defined as “EGR deactivation due to NOx excess”. It is set when the Powertrain Control Module (PCM) detects that the level of nitrogen oxides (NOx) in the exhaust gas exceeds the maximum allowable threshold. Exceeding occurs as a result of the exhaust gas recirculation system being disabled.

Fault code P2BAC – NOx exceedence – deactivation of EGR

The P2BAC code is informational in nature and is only set to alert the driver that the exhaust gas recirculation system is disabled. This error will always be accompanied by one or more other codes related to the exhaust system, and correcting these codes will also eliminate P2BAC.

The purpose of the exhaust gas recirculation system is to introduce a metered amount of exhaust gas into the engine along with the air/fuel mixture. To reduce the combustion temperature (below 2700 °F) above which harmful NOx compounds are produced as a result of the combustion process.

In practice, the introduction of exhaust gas has the effect of extinguishing the combustion flame, this effect limits or prevents the formation of NOx.

In most cases, the PCM has the ability to deactivate the EGR system in the event of malfunctions, failures or problems. Which do not allow the EGR system to be operated effectively.

If the EGR system is deactivated for any reason, an excessive amount of NOx is sure to be generated during the combustion process. Therefore, the PCM will set the P2BAC code and turn on the warning lamp as a warning that the EGR system has been deactivated or disabled.

Symptoms of vehicle malfunctions

The main signal that an error P2BAC has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. Check engine control lamp on the control panel will light up (the code will be recorded in the memory as a malfunction).
  2. Black smoke from the exhaust pipe.
  3. Reduced engine power.
  4. Increased fuel consumption.

The severity of the stored P2BAC code depends on what related codes are present. This error itself has no symptoms, but is only a notification that the EGR is off.

Factors that can cause this error code

The error code P2BAC can mean that one or more of the following problems have occurred:

  • Incorrect DPF or NOx recovery fluid.
  • Insufficient recovering fluid.
  • Ineffective DPF recovery or NOx trapping due to driving habits.
  • Defective catalytic converter.
  • Defective DPF, NOx trapping, or oxygen O₂ sensor.
  • Sometimes the cause is a defective PCM module or its programming error.

How to fix or reset OBD-2 code P2BAC

Some suggested steps for troubleshooting and fix the error code P2BAC:

  1. Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances the P2BAC error occurred.
  2. Clear the error codes from the computer memory and test drive the vehicle to see if the fault appears again.
  3. Note which DPF or NOx recovery fluid is being used.
  4. Test the oxygen O₂ sensors as well as the catalytic converter.
  5. If no problems are found anywhere, check and, if necessary, replace the Powertrain Control Module (PCM).

Diagnose and repair of problems

The first thing to do is to check the maintenance bulletins (TSB) for your particular vehicle. Your P2BAC problem may be a known problem with a known fix issued by the manufacturer. This can save you time and money during diagnosis.

Next, make sure there is enough and the correct type of DPF regeneration or NOx capture fluid present in your vehicle. This code is a direct result of a stored DPF, NOx catcher or O₂ sensor code.

Therefore, you must first diagnose and correct any other codes that are present. Correcting a DPF or NOx trap regeneration fluid problem can eliminate the conditions that cause these types of codes to persist.

Certain driving habits can also affect DPF and NOx trap regeneration. Short trips and trips that do not require efficient engine loading may not provide sufficient DPF or NOx trap regeneration.

Use the appropriate diagnostic information for the codes that accompany the P2BAC error, diagnose and repair them first. After that, this problem should also disappear.

Trying to correct this error without correcting the other stored codes may be a waste of time.

On which vehicles does this problem occur most frequently

Fault code P2BAC can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Chevrolet
  • Dodge (RAM)
  • Ford (Transit)
  • GMC
  • Mercedes-Benz (Sprinter)
  • Scania
  • Volkswagen (Crafter)

Fault code P2BAC can sometimes be found with other errors. The most common are the following: P00AF, P014C, P014D, P0191, P0542, P2010.


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