Technical Description of OBD-II Trouble Code
Range/Performance Issue with Reductant/Regeneration Supply Control Circuit
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to many OBD-II vehicles (1996-newer). This includes vehicles from Dodge, Chevrolet, GMC, Ford, and others. While it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration.
A stored code P202F indicates that the powertrain control module (PCM) has detected insufficient activity in the control circuit for the reductant/regeneration supply pump.
The catalyst system is responsible for reducing almost all exhaust emissions, although certain applications also have a NOx trap.
Exhaust gas recirculation (EGR) systems go a step further in reducing NOx. However, larger and more powerful diesel engines today cannot meet strict federal (U.S.) emission standards with just the EGR, diesel particulate filter/catalytic converter, and NOx trap. This is why selective catalytic reduction (SCR) systems were developed.
SCR systems inject a reductant compound or diesel exhaust fluid (DEF) into the exhaust before the diesel particulate filter, NOx trap, and/or catalytic converter using the reductant injection valve (solenoid). The precisely timed DEF injection raises the temperature of the filtration element, allowing it to function more efficiently. This improves the longevity of the filtration element and reduces harmful exhaust emissions released into the atmosphere. The entire SCR system is monitored and controlled by either the PCM or a stand-alone controller that interacts with the PCM. The controller monitors the O2, NOx, and exhaust temperature sensors, among other inputs, to determine the appropriate time for DEF (reductant) injection. Precise DEF injection is crucial for maintaining exhaust temperature within acceptable parameters and optimizing pollutant filtration.
The reductant/regeneration supply pump pressurizes the DEF in the liquid reductant system for use when needed. The PCM monitors the supply pump voltage for consistent fluctuation and load percentage. The PCM also monitors one or more pressure sensors in the reductant supply system to detect any leaks.
If the PCM detects voltage variation on the reductant/regeneration supply circuit that is outside allowable parameters, it will store a code P202F and may illuminate a malfunction indicator lamp (MIL). Multiple ignition cycles with a failure may be necessary for MIL illumination.
What is the severity of this DTC?
A stored code P202F should be considered severe and addressed as soon as possible. It could disable the SCR system, and catalyst damage may occur if the conditions contributing to the stored code are not rectified promptly.
What are some of the symptoms of the code?
Symptoms of a P202F trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P202F troubleshooting steps?
To diagnose a code P202F, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information.
You can use your vehicle information source to find a technical service bulletin (TSB) that matches the vehicle’s year, make, and model, as well as the engine size, stored code/s, and exhibited symptoms. If you find a relevant TSB, it may provide helpful diagnostic information.
Use the scanner connected to the vehicle diagnostic connector to retrieve all stored codes and relevant freeze frame data. It is advisable to write down this information before clearing the codes and then test-drive the vehicle until the PCM either enters readiness mode or the code is reset.
If the PCM enters readiness mode at this point, the code is intermittent and may be more challenging to diagnose. In such cases, the conditions contributing to the stored code may need to worsen before an accurate diagnosis can be made.
If the code is immediately reset, the next step in your diagnosis will involve searching your vehicle information source for diagnostic flowcharts, connector pin-out charts, connector face views, and component testing procedures/specifications.
Step 1
Use the DVOM to test the reductant tank supply pump according to the manufacturer’s specifications. Any components that do not test within the maximum allowable parameters should be considered defective.
Step 2
Use your vehicle diagnostic information source and the DVOM to test the voltage of the reductant supply pump (usually battery voltage) when the pump is activated. If current conditions do not allow activation, you can use the scanner to manually activate the pump.
Step 3
If the reductant supply pump is functioning properly, use the DVOM to test the input and output signal circuits from the fuse panel, PCM, and ignition switch. Disconnect all controllers before using the DVOM for testing.
