Fuel Pump Relay, Checking

Fuel Pump Relay, Checking

Special tools, testers and auxiliary items required
- Multimeter.
- Wiring diagram.

Test requirements
- Fuse S132OK.
- Fuse S134OK.
- 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.

Start diagnosis
- Using a Multimeter, check the following wiring connection for voltage.

Fuel Pump (FP) Relay Measure to
J17 socket
17/30 Engine Ground (GND)

Specified value: 12.5 V

If the specified value was not obtained:
- Check the Fuel Pump (FP) Relay J17 socket 17/30 to the Battery A B (+) terminal for an open circuit or short to Ground (GND).
- 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:

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

Fuel Pump (FP) Relay Measure to Ignition/Starter Switch D terminal
J17 socket
22/50 1/50
19/86 6/15

Specified value: 12.5. battery voltage.

- Switch the ignition off.

If the specified value was not obtained:
- 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) Relay J17 socket 16/Mot to the Motronic Engine Control Module (ECM) J220 electrical harness connector terminal 65 for resistance.

Specified value: 1.5 Ohms.

If the specified value was not obtained:
- Check the Fuel Pump (FP) Relay J17 socket 16/Mot to the Motronic Engine Control Module (ECM) J220 electrical harness connector terminal 65 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) Relay J17.
- Perform a road test to verify repair.

If the fault does not return:
Repair complete, Generate readiness code. 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 Motronic Engine Control Module (ECM) J220.
- Assembly is performed in the reverse of the removal.

Final procedures
After the repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If the DTC memory was erased, generate readiness code.

End diagnosis.