Fuel Pump Control Module, Checking

Special tools, testers and auxiliary items required 

• Multimeter.
• Wiring diagram.

Test requirements 

• Fuse SC1 OK.
• Fuse S132 OK.
• Battery voltage at least 12.5 volts.
• All electrical consumers such as, lights and rear window defroster, switched off.

• Vehicles with automatic transmission, selector lever in position "P" or "N".
• A/C switched off.
• Ground (GND) connections between engine/transmission/chassis OK.
• Ignition switched off.

Test procedure 

• Perform a preliminary check to verify the customers complaint. Refer to → Preliminary Check 
• Remove access cover beneath the carpet on the passenger side of the luggage compartment. Refer to the appropriate service information.

Checking voltage 

Switch the ignition on.

• Using a Multimeter , check the following wiring connection for voltage.

Fuel Pump (FP) Control Module J538 Terminal	Measure to
2	B+
3	Chassis Ground (GND)

Specified value: Battery voltage

• Switch the ignition off.

If the specified value was not obtained:

• Check the Fuel Pump (FP) Control Module J538 wiring harness terminal 3 to the Battery B (+) terminal for an open circuit or short to Ground (GND).
• Check the Fuel Pump (FP) Control Module J538 wiring harness terminal 2 to the B (+) terminal for an open circuit or short to B+.
• Check the electrical harness connectors for damage, corrosion, loose or broken terminals.
• If necessary, repair the wiring connection.

If no malfunctions are found in the wiring:

• Switch the ignition on.
• Using a Multimeter , check the following wiring connection for voltage.

Fuel Pump (FP) Control Module J538 Terminal	Measure to
5	Chassis Ground (GND)

Specified value: about 5 V

• Switch the ignition off.

If the specified value was not obtained:

• Check the Fuel Pump (FP) Control Module J538 wiring harness terminal 5 to the Engine Control Module (ECM) J623 harness connector T94a, terminal 35 for an open circuit or short to Ground (GND).
• Check for an open circuit or short to Ground (GND).
• Check the electrical harness connector for damage, corrosion, loose or broken terminals.
• If necessary, repair the wiring connection.

If no malfunctions are found in the wiring:

Checking Ground (GND) 

• Using a Multimeter , check the Fuel Pump (FP) Control Module J538 wiring harness terminal 4/31 to chassis ground for resistance.

Fuel Pump (FP) Control Module J538 Terminal	Measure to
4/31	Chassis Ground (GND)

Specified value: 1.5 Ω maximum.

If the specified value was not obtained:

• Check the Fuel Pump (FP) Control Module J538 4/31 to ground connection 6 (main wiring harness) for an open circuit or a short to Battery (+).
• Check the electrical harness connector for damage, corrosion, loose or broken terminals.
• If necessary, repair the wiring connection.

If no malfunctions are found in the wiring and the voltage supply was OK:

• Replace the Fuel Pump (FP) Control Module J538. Refer to the appropriate service information .
• Perform a road test to verify repair.

If the fault does not return:

Repair complete, Generate readiness code. Refer to → Readiness Code .

• End diagnosis.

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

• Replace the Engine Control Module (ECM) J623. Refer to → Engine Control Module, Replacing .
• Assembly is performed in the reverse of the removal.

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

1. Check the DTC memory.
2. If necessary, erase the DTC memory. Refer to Diagnostic Mode 04 - Reset/Delete Diagnostic Data .
3. If the DTC memory was erased, generate readiness code. Refer to Readiness Code .