Motronic Engine Control Module (ECM) Power Supply Relay J271 , Checking

Motronic Engine Control Module (ECM) Power Supply Relay J271, Checking

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

Test requirements







- The Motronic Engine Control Module (ECM) J220 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 2/30 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 2/30 for an open circuit or a short circuit.
- Check the wiring connections for damage, corrosion, lose 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 4/86 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.
- Turn key off.
- Install the test box.

If the manufacturers test box is not being used. Perform the following step.
- Remove the Motronic Engine Control Module (ECM) J220.
- Using a Multimeter , check the Motronic Engine Control Module (ECM) Power Supply Relay J271 socket 4/86 to the Motronic Engine Control Module (ECM) J220 electrical harness connector terminal 21 for resistance.

Motronic Engine Control Motronic Engine Control Module
Module (ECM) Power Supply (ECM) J220 electrical connector
Relay J271 socket terminal test box socket
4/86 21

Specified value: 2.0 ohm 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, lose or broken terminals.
- If necessary, repair the faulty wiring connection.

Checking activation

- Switch the ignition on.
- Using a Multimeter , check the Motronic Engine Control Module (ECM) Power Supply Relay J271 socket 5/87 to Engine Ground

Motronic Engine Control Motronic Engine Control Module
Module (ECM) Power Supply (ECM) J220 electrical connector
Relay J271 socket terminal test box socket
5/87 Engine ground (GND)

Specified value: 12.5 V
- Switch the ignition off.

If the specified value was not obtained:
- Replace the Motronic Engine Control Module (ECM) Power Supply Relay J271.

If no malfunction is found in the wiring and voltage supply was not OK:
- Replace the Motronic Engine Control Module (ECM) J220.

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 of diagnosis.