Low Fuel Pressure Sensor, Checking

The following procedure requires a test drive. Observe all safety precautions. Refer to SAFETY PRECAUTIONS .

Special tools and workshop equipment required 

• Multimeter.
• Wiring diagram.

Test requirements

• Fuel Pump (FP) Control Module -J538- OK; check.
• The fuel filter OK.
• The fuses for the engine electronics OK.
• The parking brake engaged.
• The battery voltage at least 12.5 V.
• The selector lever of automatic transmission in position "P" or "N".
• All electrical consumers switched off (radiator fan must NOT run during test).
• A/C switched off.
• The fuel tank at least ¹ /₄ filled.
• The ignition switched off.

Test procedure 

-- Observe safety precautions. Refer to SAFETY PRECAUTIONS 

-- Observe Clean Working Conditions. Refer to CLEAN WORKING CONDITIONS 

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .

Checking voltage 

-- Disconnect the electrical harness connector from the Low Fuel Pressure Sensor -G410-.

-- Switch the ignition on.

-- Using a multimeter, check the electrical harness connector for voltage.

Harness connector Terminal	Specified value
1 to Battery positive (+)	Battery voltage
2 to ground	Battery voltage
3 to ground	Near 5 V

-- Switch the ignition off.

If specified value is obtained:

-- Replace the Low Fuel Pressure Sensor -G410-

If the specified value was not obtained:

Checking wiring connections 

If the manufacturers test box is being used. Perform the following step.

-- Install the test box.

If the manufacturers test box is not being used. Perform the following step.

-- Remove the Motronic Engine Control Module (ECM) -J623-. Refer to the Repair information.

Low Fuel Pressure Sensor -G410- electrical harness connector terminals	Motronic Engine Control Module (ECM) -J623- electrical connector T60 terminals or T94 or test box sockets
1	14
2	15
3	37

Specified resistance 1.5 Ω max.

If the specification is not obtained:

-- Check the wiring for an open, high resistance or short circuit to voltage or ground.

-- If necessary, repair the wiring connection.

-- Erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .

-- Perform a road test to verify repair.

If the DTC does not return:

Generate readiness code. Refer to READINESS CODE .

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:

-- Replace the Motronic Engine Control Module (ECM) -J623-. Refer to the Repair information.

-- Assembly is performed in the reverse of the removal.

Final procedures 

After repair work, the following work steps must be performed in the mentioned sequence:

1. Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .