Guide To P20F3 OBD Error Code Solutions

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The trouble code P20F3 can be elucidated as SCR NOx Pre- Catalyst Efficiency Below Threshold Bank 2. This code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made from 1996 up to present. It’s also more common among Audi, Citroen, Chevrolet, Ford, Hyundai, Nissan, Peugeot, and Volkswagen vehicles. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model, powertrain configuration type, to another.

The selective catalyst reduction (SCR) catalyst is examined to ensure it is capable of NOx conversion. The concentration of NOx upstream of the SCR is calculated depending upon the automobile’s model. It is the NOx sensor which measures the NOx concentration downstream of the SCR. These concentrations are then used to calculate the cumulative efficiency of the SCR catalyst and it is then compared to a threshold. If the cumulative efficiency would be below this threshold for a sufficient period of time then it would be an indication of a fault.

What causes this problem with the SCR NOx Pre- Catalyst Efficiency Below Threshold Bank 2?

• Faulty SCR injector
• Some issues related to the DEF fluid
• Imperfect O2, NOx, or temperature sensor
• Broken SCR system
• Installation of aftermarket or high-performance exhaust components
• The SCR controller might not be functioning properly
• There might be PCM programming error
• Quirks in the pre-catalyst exhaust

1. Engine Control Module - Most of the time it is difficult to intercept the ECM faults and thus must be checked for thoroughly. There can be a problem with the circuit or the software might have malfunctioned. Thus repair, replace or reprogram the component as per requirement.
2. Powertrain Control Module - If the PCM is faulty, it can stores wrong OBD codes and can lead to misdiagnosis. This can happen due to misinterpretation of data received from the various sensors and components which also affects the vehicle’s performance. Thus replace it immediately.
3. Diesel Exhaust Fluid Pump - If the fluid pump is physically damaged, it can result in leakages, loss of pressure and harsh shifting. Thus, the fluid pump must be replaced, if found damaged. Buy new fluid pump from us now!
4. Electronic Control Unit – If the ECU is at fault, it will not be able to read the boost converter temperatures correctly leading to underperformance. Thus, replace faulty ECU now!
5. Diagnostic Tool - Choose from our diagnostic tools collection that will come handy to detect and correct the OBD error code.

You might be thinking that how would you diagnose these problems? We at Parts Avatar Canada would help you diagnose the major symptoms easily.

Common Symptoms

• Decrease in the overall fuel efficiency
• There might be a lot of black smoke coming out from vehicle exhaust
• The engine performance might start declining
• Storage of some SCR and emission related codes

The repairs which you will have to do to correct this fault code are simply straightforward; you can surely pinpoint the necessary repairs on the basis of your diagnosis. Have a look at some common fixes:

• You must fix the defective SCR controller or programming error
• Make sure to mend the faulty SCR system parts
• Rehabilitate the defaults in the electronic control unit
• Carefully adjust the faults in the powertrain control module
• The SCR injector should be restored to working order
• Adjust the flawed exhaust temperature sensor

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Here are some steps which you should follow in order to diagnose this fault code:

• The mechanic or the technician will use a diagnostic scanner or code reader like DVOM to visually scan for the error codes in the vehicle.
• After performing a careful inspection, every of the stored codes and freeze frame data are retrieved as it can help down the way for further diagnosis process.
• If you find out that other SCR or exhaust emissions codes or exhaust temperature codes are stored, then make sure to address them before attempting to diagnose the stored P20F3.
• Repair any pre-catalyst leakages in the exhaust before attempting a diagnosis for this type of fault code.
• It is essential to have a diagnostic scanner, a digital volt/ohmmeter (DVOM), an infrared thermometer with a laser pointer, and a source of vehicle specific SCR system diagnostic information to easily diagnose the P20F3 fault code.
• Carefully locate the technical service bulletin (TSB) which would match the vehicle year, make, and model; as well as the engine size, code/s stored, and symptoms exhibited could yield helpful diagnostic information.
• A visual inspection of the SCR injection system, exhaust temperature sensors, NOx sensors, and oxygen (02) sensor harnesses and connectors should be done before starting the process of diagnosis.
• Make sure to repair or restore the burnt or faulty wiring and or connectors before proceeding.
• Then the next step would be to locate the vehicle diagnostic connector and plugging in the scanner. All stored codes should be retrieved and pertinent freeze frame data and record this information before clearing the codes.
• Then the vehicle should be taken out for a test drive until the powertrain control module would enter the readiness mode or the code is reset.
• Now if the PCM does enter readiness mode, this would mean that the code is intermittent and may be much more difficult to diagnose at this time.
• The conditions which contributed to the code being stored should be allowed to worsen before a diagnosis can be reached.
• Once the code has been reset immediately, search your source of vehicle information to get diagnostic flow charts, connector pin out charts, connector face views, along with constituent testing procedures as well as specifications.
• This information would prove to be very helpful in completing the next steps of your diagnosis.
• Carefully observe the scanner data stream to compare exhaust (pre-cat and post-cat) temperature sensor data between engine banks.
• If it detects some inconsistencies, then the exhaust temperature sensors should be tested using the DVOM. If the sensors would fail to comply with the specifications set by the manufacturer, then it would indicate that it is faulty.
• Now if all sensors and circuitry appear to be functioning as intended, then it would mean that the catalyst element is defective or there is a failure in the SCR system.

Common Mistakes When Diagnosing The P20F3 Code

• There can be some contamination in the DEF
• Negligence in the DEF injector
• Selective catalytic reduction problems