Low Fuel Pressure Sensor, Checking

Special tools and workshop equipment required 

• Multimeter.
• Wiring diagram.

Test requirements 

• The Fuel Pump (FP) Control Module -J538- OK.
• The Engine Control Module (ECM) - J623- fuses OK.
• The fuel filter OK.
• The battery voltage at least 12.5 V.
• 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 

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

Start diagnosis 

-- Remove the rear engine cover -arrows-.

Checking voltage 

-- Disconnect the Low Fuel Pressure Sensor -G410- connector.

-- Switch the ignition on.

-- Using a multimeter --, check the Low Fuel Pressure Sensor -G410- electrical harness connector for voltage.

Low Fuel Pressure Sensor -G410- electrical harness connector terminals	Specified value
1 to Battery positive (+)	Battery voltage (+)
2 to Ground (GND)	about 5 V
3 to Ground (GND)	about 5 V

-- Switch the ignition off.

If the specified values are obtained:

-- Replace the Low Fuel Pressure Sensor -G410-, note the following:

If the specified values are not obtained:

Checking wiring 

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 ENGINE CONTROL MODULE, REPLACING .

-- Using a Multimeter --, check the Low Fuel Pressure Sensor -G410- electrical harness connector terminals to the Engine Control Module (ECM) -J623- electrical harness connector T94 terminals for an open circuit according to the wiring diagram.

Low Fuel Pressure Sensor -G410- electrical harness connector terminals	Engine Control Module (ECM) -J623- electrical connector T94 terminals or test box socket
1	53
2	35
3	19

Specified value: 1.5 Ω Max.

If the specification was not obtained:

-- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).

-- Check the electrical harness connector for damage, corrosion, lose or broken terminals.

-- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

-- 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:

Repair complete, Generate readiness code. Refer to READINESS CODE .

-- End diagnosis.

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 ENGINE CONTROL MODULE, REPLACING .

-- 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 .