Technical Description of OBD-II Trouble Code
The fuel pressure regulator 2 has exceeded control limits and is too high.
What is the meaning of P229D?
P229D 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.
In my personal experience diagnosing a P229D, it has only been found in diesel powered vehicles. It indicates that the powertrain control module (PCM) detected an excessive fuel pressure sensor voltage in the electronic fuel pressure sensor/regulator during adaptive learning or relearning strategy.
The regulator in question is designated as 2. Systems with multiple electronic fuel pressure regulators often use numerical designations. The 2 may also refer to a specific bank of the engine. Refer to the manufacturer’s specifications for the vehicle in question. 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. Using input data from the fuel pressure sensor located in the fuel injector rail, the PCM constantly adjusts the pressure regulator voltage while the engine is running. Battery voltage and ground signals control a servo motor in the fuel pressure regulator, which actuates a valve to achieve the desired fuel pressure for any given situation.
Increasing voltage at the electronic fuel pressure regulator servo motor opens a valve and increases fuel pressure. Decreasing voltage closes the valve and decreases fuel pressure. The fuel pressure regulator and fuel pressure sensor are usually integrated into a single housing with one electrical connector, but they may also be separate components.
If the actual fuel pressure regulator 2 control circuit voltage is not within a certain parameter during a learning session, a P229D code will be stored and a malfunction indicator lamp (MIL) may illuminate.
A typical fuel pressure regulator:
What is the severity of this DTC?
A code P229D should be considered severe because insufficient or excessive fuel pressure can cause internal engine and catalytic converter damage and lead to various drivability issues.
What are some of the symptoms of the code?
Symptoms of a P229D trouble code may include:
What are some of the common causes of the code?
Possible causes for this code include:
What are some P229D troubleshooting steps?
To accurately diagnose a code P229D, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information.
It may save time to search for technical service bulletins (TSB) that match the stored code, vehicle information, and symptoms. This information can be found in your vehicle information source. If you find the right TSB, it may provide a quick solution to your diagnosis.
After connecting the scanner to the vehicle diagnostic port and retrieving all stored codes and freeze frame data, write down the information in case the code is intermittent. Then, clear the codes and test drive the vehicle until either the code is restored or the PCM enters readiness mode.
If the PCM enters readiness mode at this point, diagnosing the code may be more difficult because it is intermittent. The condition that caused the P229D to be stored may need to worsen before an accurate diagnosis can be made. If the code is restored, continue with the diagnosis.
You can obtain connector face views, connector pinout charts, component locator charts, wiring diagrams, and diagnostic flow charts for the code and vehicle in question from your source of vehicle information.
Perform a visual inspection of the related wiring and connectors. Repair or replace any wiring that is cut, burned, or damaged.
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 or defective fuses before retesting.
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 with the DVOM. If either of them does not comply with the manufacturer’s specifications, consider it 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.
