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

Motronic ECM Power Supply Relay -J271-, Checking







Special tools and workshop equipment required

- V.A.G 1526 A.
- V.A.G 1594 A.
- V.A.G 1598/31.

NOTE: The Motronic ECM power supply relay -J271- supplies the ignition coils with output stages as well as the ECM on Pin 121 with power.

Test sequence







- Remove engine cover -arrows-.







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







- Connect multimeter as follows to measure voltage.

Connector Measure to

1 Engine Ground (GND)

- 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 -2-.







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

Relay carrier in electronics box, plenum Connection of
chamber, position 2 ignition coils.
terminal terminal

8 1

- Repair open circuit, if necessary.

If 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.

Relay carrier in electronics Measure to
box, plenum chamber, position 2
terminal

2 Engine ground(GND)
3 Engine ground (GND)

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

If specified value is not obtained:
- Check wiring connections.

Checking activation







- Connect multimeter as follows to measure voltage.

Relay carrier in electronics Measure to
box, plenum chamber, position 2
terminal

6 Battery positive (B+)

- Switch ignition on.
- Specified value: approx. battery voltage (B+).

If specified value is not obtained:
- Switch ignition off.
- Connect test box V.A.G 1598/31 to wiring harness for ECM; do not connect ECM.







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

Relay carrier in electronics Test box VAG
box, plenum chamber, position 2 1598/31
terminal Socket

6 21

- Repair any open/short circuit as necessary.

If no fault is found:
- Replace power supply relay -J271-.