ECM Power Supply Relay, Checking

ECM Power Supply Relay, Checking





Special tools, testers and auxiliary items required

• Multimeter (V.A.G 1526 A)

• Connector test kit (V.A.G 1594 A)

• Test box (VAG1598/31)

• The Motronic ECM power supply relay (J271) supplies the ignition coils with output stages as well as the ECM on Pin 121 with power.

Work sequence

- Remove engine cover (arrows).





- Disconnect 4-pin connector - 1 - from ignition coil - 2 -.





- Connect multimeter as follows to measure voltage.









- Switch ignition on.

• Specified value: approx. battery voltage (B+)

If specified value is not obtained:

- Switch ignition off.

- Remove rubber seal of plenum chamber cover in direction of (arrow).





- Remove plenum chamber cover - 1 - from front.

- Pry off both trim caps - 3 - with a screwdriver.





- Loosen hex nuts - 4 - several turns.

- Release wiper arms - 2 - from pivot shaft by tilting them slightly.

- Remove hex nuts completely and remove wiper arms.

- Remove retaining clips - 1 - and remove air cowl grille - 5 -.

- Remove cover for electronics box (plenum chamber) - arrows -.





- Lift off ECM retaining clip using a screwdriver (arrow) and move module to side.





- If installed, unclip Transmission Control Module (TCM) retaining clip and move module to one side.

- Disconnect power supply relay - 3 -.





- Check for open circuit in following wiring according to wiring diagram:









- Repair open circuit, if necessary.

If the wiring is OK:

- Check voltage supply of Motronic ECM power supply relay (J271).

- Check activation of Motronic ECM power supply relay (J271).

Checking power supply

- Connect multimeter as follows to measure voltage.









• Specified value: approx. battery voltage (B+)

If specified value is not obtained:

- Check wiring connections.

Checking activation

- Connect multimeter as follows to measure voltage.









- Switch ignition on.

• Specified value: approx. battery voltage (B+)

If specified value is not obtained:

- Switch ignition off.

- Connect test box (VAG1598/31) to wiring harness for ECM; do not connect ECM => [ Electrical Testing, with Test Box VAG 1598/31 ] Electrical Testing, With Test Box VAG 1598/31.

- Check for open circuit, short to positive, or short to ground in following wiring connection(s):









- Repair any open/short circuit as necessary.

If no malfunction is found:

- Replace Motronic ECM power supply relay (J271 ).