Signal Too High

Signal too high

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).

- 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 roughly 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 the connectors between the fuel pump (FP) control module and the fuel pump (FP). Check for contact resistance. Check for oxidation.
Remedy as necessary.
Try a new fuel pump (FP) control module if no fault is found during the above fault-tracing.

Other information
- 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.




- Connect the manometer. See: Fuel pressure gauge Fuel Pressure Gauge
- 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, this indicates incorrect function.









Is the function OK?

Yes - VERIFIED

No - VERIFICATION FAILED

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VERIFIED - FAULT FOUND

VERIFICATION FAILED - Fault-tracing information

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Verification




Verification

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




- Run the engine to operating temperature. Allow the engine to idle.
- air conditioning (A/C) off
- Read off the fuel pressure and the fuel pressure desired value.
- Start the quick test when the engine is running at idling.
During the course of the quick test, the control module will steer the pressure to different target values in different stages (400, 500, 600 and finally 700 kPa), after which the pressure will be decreased in stages to the same pressure. Each stage lasts for approximately 5 seconds.

Note! Because the by-pass valve in the fuel pump (FP) will be open at approximately 650 kPa, the pressure will not go higher than this.

Hint: The illustration to the left shows an example of normal regulation.

- The upper digital display and the graphic display (red font color) indicate the absolute fuel pressure, calculated from the fuel pressure sensor
- The central digital display and the graphic display (blue font color) indicate the control module target value for the absolute fuel pressure
- The lower digital display indicates the relative fuel pressure (white font color), calculated from the fuel pressure sensor and the atmospheric pressure sensor (= absolute pressure minus atmospheric pressure). If a manometer is connected during the test, it must indicate this pressure.
Check that the value for absolute fuel pressure is the same as the target value for absolute fuel pressure. If the values are not the same, this indicates a fault in the pressure regulation. The values may differ during the quick test when the target value is changed. This is due to sluggishness in the fuel regulation and is normal. In some cases, it can take up to 5 seconds before the fuel pressure reaches the target value for the fuel pressure.









Is the function OK?

Yes - VERIFIED

No - VERIFICATION FAILED

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VERIFIED - FAULT FOUND

VERIFICATION FAILED - Fault-tracing information

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Fault-tracing information

Attempt New Test - Checking the fuel pressure sensor

FAULT-TRACING FAILED - No Fault Found

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