Technical Description of OBD-II Trouble Code
The fuel pressure regulator 2 has exceeded control limits, resulting in pressure that is too low.
What is the meaning of P229A?
P229A 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 P229A code has only been applicable to diesel powered vehicles. It indicates that the powertrain control module (PCM) has detected a low voltage signal from the control circuit of the electronic fuel pressure regulator, indicating insufficient fuel pressure.
The “2” in the code refers to the specific regulator being referenced. Some systems with multiple electronic fuel pressure regulators use numerical designations. The “2” may also indicate a certain bank of the engine. It is important to consult the manufacturer’s specifications for the specific vehicle. High pressure diesel fuel injection systems should only be serviced by qualified personnel.
The PCM (or some type of 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 voltage of the pressure regulator to maintain the desired fuel pressure for different situations. A servo motor controlled by battery voltage and ground signals actuates a valve in the fuel pressure regulator to achieve the desired fuel pressure level. The fuel pressure regulator and fuel pressure sensor are often integrated into a single housing, but can also be separate components.
If the actual voltage of the fuel pressure regulator 2 control circuit exceeds a certain parameter determined by the PCM, and the actual fuel pressure is not within specifications, a P229A 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 P229A should be considered severe because insufficient or excessive fuel pressure can cause damage to the internal engine and catalytic converter, as well as lead to various drivability issues.
What are some of the symptoms of the code?
Symptoms of a P229A trouble code may include:
What are some of the common causes of the code?
Possible causes for this code include:
What are some P229A troubleshooting steps?
To accurately diagnose a code P229A, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information.
It may be helpful 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 often 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. 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, diagnosing the code may be more difficult because it is intermittent. The condition that caused the P229A code 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 wiring and connectors related to the code. 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 using the DVOM. If either component does not comply with the manufacturer’s specifications, it should be 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.
