Technical Description of OBD-II Trouble Code
The fuel pressure regulator 2 has exceeded its learning limits and is too low.
What does P229C mean?
P229C is a generic powertrain code that applies to many OBD-II vehicles (1996-newer), including Volkswagen, GMC, Chevrolet, Cadillac, Ford, BMW, and others. The exact repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
In my personal experience, the P229C code has only been observed in diesel powered vehicles. It indicates that the powertrain control module (PCM) has detected insufficient fuel pressure sensor voltage in the electronic fuel pressure sensor/regulator during adaptive learning or relearning strategy.
The “2” in the code refers to the specific regulator being referenced. Some systems use numerical designations for multiple electronic fuel pressure regulators, and the “2” may also indicate a certain bank of the engine. Refer to the manufacturer’s specifications for the vehicle in question. It is important to note that high pressure diesel fuel injection systems should only be serviced by qualified personnel.
The PCM or integrated diesel controller monitors and controls the electronic fuel pressure regulator. It adjusts the pressure regulator voltage based on input data from the fuel pressure sensor, which is located in the fuel injector rail. A servo motor controlled by battery voltage and ground signals actuates a valve in the fuel pressure regulator to achieve the desired fuel pressure for different situations.
If the actual fuel pressure regulator 2 control circuit voltage is not within a certain parameter during a learning session, a P229C code will be stored and the malfunction indicator lamp (MIL) may illuminate.
A typical fuel pressure regulator:
What is the severity of this DTC?
A code P229C should be considered severe because insufficient or excessive fuel pressure can cause internal engine and catalytic converter damage, as well as various drivability issues.
What are some of the symptoms of the code?
Symptoms of a P229C trouble code may include:
What are some of the common causes of the code?
Possible causes for this code include:
What are some P229C troubleshooting steps?
To accurately diagnose a P229C code, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and reliable vehicle information.
Start by searching for technical service bulletins (TSB) that match the stored code, vehicle information, and symptoms. This information can be found in your vehicle information source and may provide a quick solution to your diagnosis.
Connect the scanner to the vehicle diagnostic port and retrieve all stored codes and freeze frame data. Write down the information in case the code is intermittent. Clear the codes and test drive the vehicle until the code is restored or the PCM enters readiness mode.
If the PCM enters readiness mode, the diagnosis may be more difficult as the code is intermittent. The condition that caused the P229C code to be stored may need to worsen before an accurate diagnosis can be made. If the code is restored, continue with the diagnosis.
Refer to your vehicle information source for connector face views, pinout charts, component locator charts, wiring diagrams, and diagnostic flow charts specific to the code and vehicle in question.
Perform a visual inspection of the wiring and connectors related to the code. Repair or replace any damaged wiring.
Use the DVOM to test the voltage and ground circuits at the electronic fuel regulator (2) and fuel pressure sensor(s). If no voltage is detected, check the system fuses and replace any blown fuses. Retest the circuits.
If voltage is detected, test the corresponding circuit at the PCM connector. If no voltage is detected there, suspect an open circuit between the sensor and the PCM. If voltage is present, suspect a defective PCM or PCM programming error.
Test the fuel pressure regulator and fuel pressure sensor using the DVOM. If either component does not comply with the manufacturer’s specifications, it is considered defective.
If the fuel regulator (2) and sensor(s) appear to be functioning properly, use a manual fuel pressure gauge to test the actual fuel pressure at the rail and try to replicate the failure condition.
