Audi Fuel System: MIL On/Multiple Low Fuel Pressure DTCs - P008a00

Audi Fuel System: MIL On/Multiple Low Fuel Pressure DTCs

Due to fuel intrusion into the low-pressure ­system fuel pressure sensor (G410), a false signal may be sent to the controller, resulting in a reading that is out of tolerance.

Model: 2007 Audi A4 Sedan V6-3.2L

Scenario: The MIL is on and one or more of the following DTCs is stored in the engine control module (ECM) J623.
• P310B00: Low fuel pressure regulation; fuel ­pressure outside specification.
• P129F00: Low pressure fuel system pressure too high.
• P008B00 Low pressure fuel system pressure too high.
• P129E00: Low pressure fuel system pressure too low.
• P008A00: Low pressure fuel system pressure too low.
• P254000: Low pressure fuel system sensor ­circuit range/performance.
• P008700: Fuel rail/system pressure too low.

Tip: Comparing Measured Value Block 103 with 106 is not an accurate method for diagnosing a G410. In order to diagnose a G410 accurately, use a mechanical gauge and compare results with the low-side fuel pressure Actual Value in Measured Value Block 103.

Service Recommendation:

Audi fuel system1. Verify that the customer did not run out of fuel at the time that the DTCs were stored. If the vehicle did have a low fuel level, DTCs P310B00, P129E00, and/or P008A00 may be accompanied by DTC P125000. If DTC P125000 is present, it’s likely that the faults occurred due to a low fuel level and are not related to a malfunction of the G410.

2. Follow GFF for each DTC.

3. To check the G410, measure the fuel pressure with a mechanical gauge, using the following method:
a. Start the engine and allow it to idle for at least one minute.
b. Stop the engine, but keep the ignition on.
c. Measure the actual low-side fuel pressure on the low-pressure supply line in the engine ­compartment (see Fig. 1).

4. To calculate the adjusted gauge measurement value, add 1 bar to the value obtained from the mechanical gauge.

5. Compare the adjusted gauge measurement value to the actual value stored in MVB 103 field 1.

Audi fuel system6. If the MVB 103 field 1 value deviates more than +/- 1.0 bar from the adjusted gauge measurement value, then the DTC was likely triggered by a faulty G410 low-side fuel pressure sensor. Document the adjusted gauge measurement value and MVB value on the repair order, then perform the sensor replacement procedure.

Sensor Replacement Procedure:

1. Replace the G410 low-side fuel pressure ­sensor (Fig. 2).

2. Clear the DTCs and verify that the problem was eliminated.

3. Run Basic Settings 103 to adapt the system.

4. Do not replace the high-pressure fuel pump, electrical fuel pump, fuel pump control module or fuel filter unless the problem persists and ­further diagnosis indicates a malfunction of any of these components.

Courtesy of ALLDATA.

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