Audi Fuel Issue

This bulletin applies to 2006 Audi Cabriolet A4, S4 and RS4 models where the MIL is on and the technician finds DTCs P310B, P129F, P008B, P129E, P008A, P2540 and/or P0087.

P310B (Low pressure fuel system regulation, fuel pressure outside tolerance)
P129F or P008B (low pressure fuel system, pressure too high)
P129E or P008A (low pressure fuel system, pressure too low)
P2540 (low pressure fuel system, pressure out of range)
P0087 (rail fuel pressure system, pressure too low)

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. Comparing Measure Value Block 103 with 106 is not an accurate method to diagnose low-side fuel pressure sensor G410.

In order to diagnose the sensor G410 accurately, use a mechanical gauge and compare results with the low-side fuel pressure actual value in measured value block 103.

Verify that the customer did not run out of fuel at the time the DTCs were stored.

P310B and/or P129E/P008A may be accompanied by P1250. If so, it is likely the faults occurred due to a low fuel level and not a malfunction of the G410 sensor.

To check the low side fuel pressure sensor G410, measure the fuel pressure with a mechanical gauge using the following method:

a. Start the engine and allow idling for at least one minute.

b. Stop the engine.

c. Keep the ignition on.

d. Measure actual low side fuel pressure via the mechanical gauge (VAG 1318) on the low pressure supply line in the engine bay.

Add 1 bar to the value obtained from the mechanical gauge to calculate the adjusted gauge measurement value.

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

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 (P/N 06E 906 051 K). In this case, document the adjusted gauge measurement value and MVB value on the repair order and perform sensor replacement.

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