Error Code P20F1: What It Means & What To Do?

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The trouble code P20F1 can be explicated as SCR NOx Pre-Catalyst - Over Temperature Bank 2. This trouble code is generic, which would mean that it can apply to all the vehicles which are equipped with the OBD-II or the vehicles which are made since 1996 up to the present. The specifications on the definition, the troubleshooting steps as well as repairs can always vary from one vehicle make to another. This can happen because of a lot of reasons and the mechanic should diagnose the specific cause for this code.

It is the engine control module which would examine the temperature for the selective catalyst reduction system (SCR) system. This trouble code would be set by the ECM when the temperature for the selective catalyst reduction system (SCR) system would not be as per the parameters set by the manufacturer.

What causes this problem with the SCR NOx Pre-Catalyst - Over Temperature Bank 2?

• Some issues related to the installation of aftermarket or high-performance exhaust components
• Unusable SCR controller or programming error
• Imperfect or insufficient DEF fluid
• Leakage in the pre-catalyst exhaust
• Broken SCR system
• Defective SCR injector
• Quirks in the exhaust temperature sensor

1. Engine Control Module - The solenoid might cause a short in the engine control module because of corrosion in the solenoid or the wire running from the solenoid to the ECM harness.
2. Diesel Exhaust Fluid Pump - The fluid pump needs to work properly if the transmission system has to perform. If it is not functioning, the transmission may slip and cause harsh shifts too. Thus replace faulty pump now and buy a new one from us!
3. Electronic Control Unit – The ECU power management control module keeps in check the hybrid battery charging functions. If the ECU is faulty, the battery pack will not be able to properly get charged and thus, the ECU might need replacement.
4. Powertrain Control Module - A trouble with the PCM would mean that it is unable to determine the right fuel mixture and would send the car engine either more or less fuel than it requires. Now when the engine gets more, the carbon emission would increase and fuel economy would drop. In case of the opposite, the engine will choke, stutter, and might start stalling sometimes.
5. Diagnostic Tool – Usually any OBD code problem requires deep insight into the problem and high grade tools in order to fix it properly. Thus, buy quality diagnostic tools form us!

It is essential to know the symptoms of an issue as only then you would be able to solve the problem. So that’s why we have listed out some major symptoms of OBD Code P20F1 here:

Common Symptoms

• The overall engine performance might start declining
• Decrease in the fuel efficiency
• A lot of black smoke might start coming out from vehicle exhaust
• Some SCR and emission related codes might appear

If you wish to correct this fault code, then you have to follow certain steps. Correcting a problem needs your careful attention. Here are some ways with the help of which you will be able to correct the OBD Code P20F1:

• You must fix the defective exhaust temperature sensor
• Make sure to mend the faulty SCR controller or programming error
• Repair or replace the quirky electronic control unit
• Rehabilitate the defaults in the powertrain control module
• The malfunctioning SCR injector should be repaired or replaced as per the need
• Recondition the non-functioning SCR system parts

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If you want to easily diagnose this trouble code, then you must follow the steps which are mentioned here as below:

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 P20F1.

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 P20F1 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 P20F1 Code

• DEF contamination related issues

• Quirks in the DEF injector
• Issues related with the selective catalytic reduction