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P229C Fuel Pressure Regulator 2 Exceeded Learning Limits - Too Low

OBD-II Trouble Code Technical Description

Article by
Stephen Darby
Stephen Darby
ASE Certified Technician

总裁俱乐部appFuel Pressure Regulator 2 Exceeded Learning Limits - Too Low

What does P229C mean?

总裁俱乐部appThis diagnostic trouble code (DTC) is a generic powertrain code and applies to many OBD-II vehicles (1996-newer). That may include but is not limited to vehicles from Volkswagen, GMC, Chevrolet, Cadillac, Ford, BMW, etc. Although generic, the exact repair steps may vary depending on year, make, model and powertrain configuration.


 

总裁俱乐部appIn my personal experience diagnosing a P229C, it has applied exclusively to diesel powered vehicles. It has also meant that the powertrain control module (PCM) had detected an insufficient degree of fuel pressure sensor voltage in the electronic fuel pressure sensor/regulator during periods when the PCM attempted to carryout adaptive learning (or relearning) strategy.

The regulator in question had been designated with a 2. Systems which utilize multiple electronic fuel pressure regulators often use a numerical designation. The 2 may also refer to a certain bank of the engine. Check manufacturer's specifications for the vehicle in question. High pressure diesel fuel injection systems should be serviced by qualified personnel ONLY.

总裁俱乐部appThe PCM (or some type of integrated diesel controller) monitors/controls the electronic fuel pressure regulator. Using input data from the fuel pressure sensor (located in the fuel injector rail), the PCM adjusts pressure regulator voltage constantly when the engine is running. Battery voltage and ground signals are used to control a servo motor (in the fuel pressure regulator) which actuates a valve used to ensure that the desired level of fuel pressure may be achieved for any given situation.

总裁俱乐部appWhen voltage is increased at the electronic fuel pressure regulator servo motor, a valve is opened, and fuel pressure is increased. Decreased voltage at the servo causes the valve to close and fuel pressure is decreased. The fuel pressure regulator and fuel pressure sensor are most frequently integrated into a single housing (with one electrical connector) but may also be separate components.

If actual fuel pressure regulator 2 control circuit voltage (pressure) which is not within a certain parameter during a learning session, a P229C will be stored and a malfunction indicator lamp (MIL) may be illuminated.

A typical fuel pressure regulator:
P229C Injection Control Pressure Sensor

What is the severity of this DTC?

总裁俱乐部appSince insufficient/excessive fuel pressure may cause internal engine and catalytic converter damage and lead to various drivability issues, a code P229C should be categorized as severe.

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?

Causes for this code may include:

What are some P229C troubleshooting steps?

总裁俱乐部appYou will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of reliable vehicle information in order to accurately diagnose a code P229C.

总裁俱乐部appYou may save yourself time by searching for technical service bulletins (TSB) that replicate the code stored, vehicle (year, make, model, and engine), and symptoms exhibited. This information may be found in your vehicle information source. If you find the right TSB, it could yield a speedy solution to your diagnosis.

After you connect the scanner to the vehicle diagnostic port and retrieve all stored codes and pertinent freeze frame data, write the information down (in case the code proves to be an intermittent one). After that, clear the codes and test drive the vehicle until one of two things happens; the code is restored or the PCM enters readiness mode.

The code may be more difficult to diagnose if the PCM enters readiness mode at this point, because the code is intermittent. The condition which caused the P229C to be stored may need to worsen before an accurate diagnosis can be made. If the code is restored, continue with the diagnosis.

总裁俱乐部appYou may obtain connector face views, connector pinout charts, component locator charts, wiring diagrams, and diagnostic flow charts (pertaining to the code and vehicle in question) using your source of vehicle information.

总裁俱乐部appPerform a visual inspection of related wiring and connectors. Repair or replace wiring that has been cut, burned, or damaged.

Use the DVOM to test voltage and ground circuits at the electronic fuel regulator (2) and fuel pressure sensor/s. If no voltage is detected, check system fuses. Replace blown or otherwise defective fuses as required and retest.

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 in question and the PCM. If voltage is discovered there, suspect a defective PCM or PCM programming error.

Test the fuel pressure regulator and the fuel pressure sensor with the DVOM. If either of them do not comply with manufacturer's specifications, consider it defective.

总裁俱乐部appIf the fuel regulator (2) and sensor/s appear to be functioning properly, use a manual fuel pressure gauge to test actual fuel pressure at the rail in an effort to duplicate the failure condition.

Related DTC Discussions

Need more help with a P229C code?

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NOTE: This information is presented for information purposes only. It is not intended as repair advice and we are not responsible for any actions you take on any vehicle. All information on this site is copyright protected.

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