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

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

Special Tools and Equipment







- VAG1526A
- VAG1594A
- VAG1598/31


NOTE: The motronic Engine Control Module (ECM) voltage supply relay -J271- supplies voltage to the ignition coils with power output stages and the Engine Control Module (ECM) at pin 121.


Test sequence







- Remove engine cover (arrows).







- Disconnect the 4-pin harness connector -1- at one of the ignition coils -2-.







- Connect multimeter for voltage measurement as follows.







- Switch ignition on.







- Specification: approx. battery voltage

If specified value is not obtained:
- Switch ignition off.
- Pull off rubber seal of plenum chamber cover in direction of arrow.
- Remove cover -1- toward front.







- Remove Heater Core E-box cover (arrows).







- Disconnect voltage supply relay -3-.







- Check the following connection for open circuit according to wiring diagram:







- Repair open circuit if necessary.

If wire connection is OK:
- Check voltage supply of motronic Engine Control Module (ECM) voltage supply relay -J271-.
- Check activation of motronic Engine Control Module (ECM) voltage supply relay -J271-.

Checking voltage supply







- Connect multimeter for voltage measurement as follows.







- Specification: approx. battery voltage

If specified value is not obtained:
- Check the wire connection between central electronics and voltage supply relay for open circuit.

If no malfunctions are found in wires:
- Replace central electronics.

Checking activation







- Connect multimeter for voltage measurement as follows.







- Switch ignition on.
- Specification: approx. battery voltage

If specified value is not obtained:
- Switch ignition off.
- Connect VAG1598/31 test box at wiring harness to Engine Control Module (ECM), do not connect ECM.







- Check the following wire connection for open circuit and short circuit to Ground (GND) and B+:







- Repair open circuit or short circuit if necessary.

If no malfunctions are detected:
- Replace motronic Engine Control Module (ECM) voltage supply relay -J271-.