Manufacturer's Scan Tool

ECM Power Supply Relay, Checking

Special tools, testers and auxiliary items required

• (VAG1526A)

• (VAG1594A)

• (VAG1598/31)

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

Test sequence

- Disconnect cover - 1 - on left in engine compartment.





- Unbolt coolant expansion tank (arrow).





- Disconnect electrical wiring to Engine Coolant Level (ECL) warning switch (F66) on bottom of expansion tank.

- Lay coolant expansion tank with connected coolant hoses - 1 - to - 3 - aside.

- Remove bolts (arrows) on left cylinder head.





- Disconnect 4-pin connectors - 4 - to - 6 - on ignition coils.

• For further testing, the multimeter is attached to an ignition coil connector.

- Connect multimeter as follows to measure voltage.









- Switch ignition on.

• Specified value: approx. battery voltage

If specified value is not attained:

- Switch ignition off.

- Pull off rubber seal of plenum chamber cover.

- Remove plenum chamber cover - 1 - toward front (arrows).





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





- Undo hex nuts - 4 - a few turns.

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

- Remove hex nuts completely and remove wiper arms.

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

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





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





- If installed, unclip transmission control module retaining clip and place control module on one side.

- Disconnect power supply relay - 2 -.





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









- Repair open circuit, if necessary.

If no wiring malfunction is detected:

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

- Check actuation of Motronic Engine Control Module (ECM) power supply relay (J271).

Checking power supply

- Connect multimeter as follows to measure voltage.









• Specified value: approx. battery voltage

If specified value is not attained:

- Check wiring connections.

Checking actuation

- Connect multimeter as follows to measure voltage.









- Switch ignition on.

• Specified value: approx. battery voltage

If specified value is not attained:

- Switch ignition off.

- Connect test box (VAG1598/31) to wiring harness for engine control module; do not connect engine control module. Refer to => [ Wiring and Component Check with Test Box VAG 1598/31 ] Wiring and Component Check With Test Box VAG 1598/31.

- Check for open circuit and short to positive or ground in following wiring connection:









- Repair any open/short circuit as necessary.

If no malfunction is found:

- Replace Motronic Engine Control Module (ECM) power supply relay (J271).