After-Run Coolant Pump: Testing and Inspection

Recirculation Pump, Voltage Supply, checking

The following test procedure is used to diagnose all fuel injectors.

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Recirculation Pump Relay (J160) fuse 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 connections between engine/transmission/chassis OK.

• Ignition switched off.

Start diagnosis

- Observe safety precautions. Refer to => [ Safety Precautions ] Safety Precautions

- Observe Clean Working Conditions. Refer to => [ Clean Working Conditions ] Clean Working Conditions

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check.

Checking voltage

- Switch the ignition on.

- Using a multimeter, check for power at socket 3 (terminal 30) of Recirculation Pump Relay (J160) to chassis ground.

Specified value: battery voltage.

- Switch the ignition off.

If the specified value was not obtained:

- Check the wiring connection from fuse 1 in Fuse Panel A (150 amp) to the Recirculation Pump Relay (J160) socket 3 (terminal 30) for an open circuit or a short circuit.

- Check the wiring connections for damage, corrosion, loose or broken terminals.

- If necessary, repair the faulty wiring connection.

If the specified value was obtained:

- Switch the ignition on.

- Using a multimeter, check the Recirculation Pump Relay (J160) socket 1 (terminal 85) to ground.

Specified value: battery voltage.

- Switch the ignition off.

If the specified value was not obtained:

- Check the wiring connection from socket 1 (terminal 85) of the Recirculation Pump Relay (J160) to fuse 9 in Fuse Panel B for an open, high resistance or short to ground.

- Check the wiring connections for damage, corrosion, loose or broken terminals.

- If necessary, repair as needed.

If the specified value was obtained:

- Using a multimeter, check the Recirculation Pump Relay (J160) socket 5 (terminal 87) to the Recirculation Pump (V50) electrical harness connector T2 terminal 1 for resistance.

Specified value: 1.5 ohms Max.

If the specification was not obtained:

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

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

- If necessary, repair the faulty wiring connection.

If the specified value was obtained:

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

- Using a multimeter, check the Recirculation Pump Relay (J160) socket 2 (terminal 86) to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T94 terminal 33 for resistance.

Specified value: 1.5 ohms Max.

If the specification was not obtained:

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

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

- If necessary, repair the faulty wiring connection.

If the specified value was obtained:

- Replace Recirculation Pump Relay (J160).

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 ] Diagnostic Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.