MOTRONIC Engine Control Module Power Supply Relay, Checking
Special tools and workshop equipment required
- multimeter.
- Wiring diagram.
Test requirements
- Fuse -SA2- 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.
-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .
Start diagnosis
-- Using a multimeter, check the following wiring connection for voltage.
| Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket | Measure to |
|---|---|
| 2 | Engine Ground (GND) |
Specified value: 12.5 V
If the specified value was not obtained:
-- Using a multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket 2 to the Fuse 2 (on fuse panel A) -SA2- 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 key on:
-- Using a multimeter, check the following wiring connection for voltage.
| Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket | Measure to |
|---|---|
| 8 | Engine Ground (GND) |
Specified value: 12.5. battery voltage.
If the specified value was not obtained:
-- Using a multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket 4 to the Fuse 2 (on fuse panel A) -SA2- 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 Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket 6 to the Engine Control Module (ECM) -J623- electrical harness connector terminal T94/19 for resistance.
Ensure key is off.
| Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket | Measure toMotronic Engine Control Module (ECM) -J623- electrical connector T94 terminals or test box socket |
|---|---|
| 6 | 19 |
Specified value: 1.5 Ω.
If the specified value was not obtained:
-- 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 theMotronic Engine Control Module (ECM) Power Supply Relay -J271-. Refer to appropriate service information.
-- Perform a road test to verify repair.
If the fault does not return:
Generate readiness code. Refer to READINESS CODE .
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 appropriate service information.
-- 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:
- Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
- If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
- If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .