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Did your OBD2 scanner register a P2BAC code? Here’s what it means, its common causes and symptoms, and how best to address the problem.
What does the P2BAC code mean?
Diagnostic trouble code (DTC) P2BAC indicates “Excess NOx – EGR Deactivation”. Since the ECM can monitor NOx as a sanity check, the ECM will normally set this code if the NOx level indicates that the EGR is not working properly. But the ECM cannot determine what the problem is from the NOx measurement alone. Usually, other codes will be present along with the P2BAC code and should be addressed first.
Note on NOx
NOx is toxic, so the exhaust gas recirculation (EGR) system was designed primarily to prevent it from forming, although even on gas burners, a catalytic converter is mounted near the engine to manage the remaining NOx that forms despite the EGR.
In modern diesel engines, there is a Selective Catalytic Reduction (SCR) converter that takes care of NOx, but diesels must be injected with a compound called diesel exhaust fluid to make the SCR catalyst in these diesels work .
To meet various OBD requirements, selective catalyst reduction systems will typically use a NOx sensor downstream of the SCR catalyst. Excessive concentrations of NOx or ammonia downstream of the SCR will trigger an OBD malfunction, as many NOx sensors are sensitive to both NOx and ammonia (from the DEF).
Depending on the SCR control strategy, another NOx sensor can be installed upstream of the SCR catalytic converter to determine the conversion rate of the SCR catalyst.
You can find out more about NOx in our technical discussion on the EGR system.
Note: The definition of the P2BAC code may vary depending on the vehicle manufacturer. Refer to the appropriate repair manual or repair database for the exact code definition.
What are the common causes of the P2BAC code?
- Critical engine performance codes are set
What are the common symptoms of code P2BAC?
- Check engine light illuminated
- Additional engine performance issues related to the other stored DTCs
How to diagnose the P2BAC code
The P2BAC code is a generic engine code that applies to various makes and models. Since it can have several causes and may come with other codes, solving them yourself is not the best option. It is best to leave the job to professionals to ensure that the problem is properly diagnosed and fixed.
How to fix P2BAC code
For do-it-yourselfers with advanced technical knowledge and hands-on experience who prefer to test and replace their vehicle’s EGR on their own, it will be helpful to rely on the appropriate repair manual or consult an online repair database.
The post P2BAC Code: Excess NOx – EGR Deactivation appeared first on In the Garage with CarParts.com.
