ECM Power Supply Relay, Checking
Special tools and workshop equipment required
- Multimeter.
- Wiring diagram.
Test requirements
- The Motronic Engine Control Module (ECM) - J623- fuses 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 sequence
-- Remove the Motronic Engine Control Module (ECM) Power Supply Relay -J271-.
Checking voltage
-- Using a Multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket 30 to Ground (GND).
Specified value: battery voltage.
If the specified value was not obtained:
-- Check the wiring connections from the Battery to the Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket 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 Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket 87 to Ground (GND).
Specified value: battery voltage.
If the specified value was 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 Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket 85 to the Motronic Engine Control Module (ECM) -J623- electrical harness connector T94 terminal 69 for resistance.
-- Ensure key is off
| Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket terminal | Motronic Engine Control Module (ECM) -J623- electrical connector T94 terminal or test box socket |
|---|---|
| 85 | 69 |
Specified value: 2.0 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, loose or broken terminals.
-- If necessary, repair the faulty wiring connection.
If no malfunction is found in the wiring:
Checking activation
-- Reinstall Motronic Engine Control Module (ECM) Power Supply Relay -J271-
-- Switch the ignition on.
-- Using a Multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket 85 to the Motronic Engine Control Module (ECM) -J623- electrical harness connector T94 terminal 69 for voltage.
| Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket terminal | Motronic Engine Control Module (ECM) -J623- electrical connector T121 terminal or test box socket |
|---|---|
| 85 | 69 |
-- Switch the ignition off.
Specified value: 0.5 V Max.
If the specified value was obtained:
-- Replace the Motronic Engine Control Module (ECM) Power Supply Relay -J271-.
If the specified value was not obtained:
-- Check the wiring connection for an open circuit, short circuit to Battery (+) or Ground (GND).
-- Check the wiring connection for damage, corrosion, loose or broken terminals.
-- If necessary, repair the faulty wiring connection.
If no malfunction is found in the wiring and voltage supply was not OK:
-- 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:
- 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 .