Technical Description of OBD-II Trouble Code
The fuel pressure regulator 2 has exceeded control limits, resulting in pressure that is too high.
What does P229B mean?
P229B 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 diagnosing a P229B, I have found it to be exclusive to diesel-powered vehicles. It indicates that the powertrain control module (PCM) has detected a high voltage signal from the control circuit of the electronic fuel pressure regulator, resulting in excessive fuel pressure.
The regulator in question is designated with a 2, which may refer to a certain bank of the engine. It is important to check the manufacturer’s specifications for the specific vehicle. It is recommended that high-pressure diesel fuel injection systems be serviced by qualified personnel only.
The PCM (or some type of 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. This adjustment is made constantly while the engine is running, using battery voltage and ground signals to control a servo motor in the fuel pressure regulator. The servo motor actuates a valve to achieve the desired level of fuel pressure for different situations. The fuel pressure regulator and fuel pressure sensor are often integrated into a single housing, but they may also be separate components.
If the actual fuel pressure regulator 2 control circuit voltage exceeds a certain parameter as computed by the PCM, and the actual fuel pressure is not within specifications, a P229B code will be stored and a malfunction indicator lamp (MIL) may be illuminated.
A typical fuel pressure regulator:
What is the severity of this DTC?
A code P229B should be categorized as 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 P229B trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P229B troubleshooting steps?
To accurately diagnose a code P229B, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information.
It is recommended to search for technical service bulletins (TSB) that match the stored code, vehicle information (year, make, model, and engine), and exhibited symptoms. This information can be found in your vehicle information source and may provide a quick solution to the 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, the diagnosis may be more difficult as the code is intermittent. The condition that caused the P229B to be stored may need to worsen before an accurate diagnosis can be made. If the code is restored, continue with the diagnosis.
Use your source of vehicle information to obtain connector face views, connector 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 related wiring and connectors, and repair or replace any cut, burned, or 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 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 discovered at the PCM connector, 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.
