Faulty Signal

Faulty signal

Checking the fuel pressure sensor

Note! If diagnostic trouble codes (DTC) for the fuel pressure sensor or atmospheric pressure sensor are stored, these diagnostic trouble codes (DTC) must be fault-traced and remedied first.

Hint: The method below is used to check whether the diagnostic trouble code (DTC) was caused by a faulty fuel pressure sensor. This can be done by comparing the fuel pressure sensor signal (displayed in VIDA) with the actual fuel pressure (displayed on a manometer connected to the wiring for the fuel injection system). This method assumes that the manometer for measuring fuel pressure is correctly calibrated.

- Connect the manometer. See: Fuel pressure gauge Fuel Pressure Gauge

Caution! The pressure in the fuel injection system can reach approximately 650 kPa when this diagnostic trouble code (DTC) is stored. Use an adapted manometer.

- Run the engine to operating temperature. Allow the engine to idle.
- Air conditioning (A/C) off.
Read off the relative fuel pressure.
The relative fuel pressure is calculated from the fuel pressure sensor and the atmospheric pressure sensor signal (= absolute pressure minus atmospheric pressure).
Check that the value on the manometer and the value displayed in VIDA are the same. If the values are different, the circuit for the fuel pressure sensor is defective.









Is the fuel pressure sensor correct?

Yes - Checking components

No - Checking the component and wiring

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Checking components
Check that the fuel level in the tank is not too low (almost no fuel).
Check the connectors between the fuel pump (FP) control module and the fuel pump (FP). Check for contact resistance. Check for oxidation.
Check the fuel lines and fuel filter for blockage and leaks.
Remedy as necessary.
Try a new fuel pump (FP) if no fault is found during the above fault-tracing.

Hint: The diagnostic trouble code (DTC) can also be caused by a defective fuel pump (FP) control module.

Other information:
- Fuel pump and level sensor unit, B5254T7, AW55-50/51SN, B5254T7, M66 Service and Repair
- Fuel pump driver module, B5254T7 Service and Repair
- Checking wiring and terminals Checking Wiring and Terminals





Continue - Verification

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Checking the component and wiring
Check the fuel pressure sensor connectors. Check for contact resistance and oxidation.
Remedy as necessary.
Try a new fuel pressure sensor if no fault is found during the above fault-tracing.

Other information
- Connecting the breakout box, B5254T7 Connecting the Breakout Box, Engine Control Module (ECM)
- Signal specification, B5254T7 Signal Specification
- Pressure sensor, fuel rail (FRP), B5254T7 Service and Repair
- Checking wiring and terminals Checking Wiring and Terminals





Continue - Verification

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Verification




Verification

Hint: After carrying out the repair, check that the fault has been remedied.




- Reinstall the connectors, components etc.
- Start the engine and run it to normal operating temperature.
Read off the fuel pump (FP) load.
Check that the engine starts and that the signal is approximately 35 % (±5 %) when the engine is idling at operating temperature.





Is the function correct?

Yes - VERIFIED

No - VERIFICATION FAILED

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VERIFIED - FAULT FOUND

VERIFICATION FAILED - Fault-tracing information

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Fault-tracing information




Information

Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.

Do you want to exit fault-tracing?

Yes - Exit fault-tracing

No - Attempt New Test

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Attempt New Test - Checking the fuel pressure sensor

FAULT-TRACING FAILED - No Fault Found

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