Motronic ECM Power Supply Relay -J271-, Checking

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

NOTE: The Motronic ECM power supply relay -J271- powers the ignition coils with output stages and the engine control module at pin 3 as well as certain other components. With the ignition on, 12 V must be applied to contact 1 of the relevant ignition coil connector.

Checking actuation wire between power supply relay and engine control module
- Switch off ignition.
- Disconnect Motronic ECM power supply relay - J271- from 3-position relay carrier.
- Connect test box V.A.G 1598/31 at wiring harness to engine control module. Actual engine control module is not to be connected. Wiring And Component Check Using Test Box V.A.G 1598/31
- Check for open circuit/short circuit in following wiring.

Test box V.A.G 1598/31,socket Power supply relay, contact
23 4

Resistance: max. 1.5 Ohm

- Eliminate open circuit in wiring/short circuit if necessary.

If no fault is found in wiring:
- Check power supply for power supply relay.

Checking power supply
- Switch off ignition.
- Connect portable multimeter for voltage measurement to contact 1 of relay socket and Ground.
- Connect portable multimeter for voltage measurement to contact 2 of relay socket and Ground.

Specification: approx. battery voltage in each case

If reading does not match specification, use wiring diagram to check power supply.

If reading matches specification:
- Check wiring between power supply relay and engine control module.

Checking wiring between power supply relay and engine control module
- Check fuse (see wiring diagram).

If no fault is found in fuse:
- Check for open circuit/short circuit in following wiring.

Test box V.A.G 1598/31, Power supply relay, relay
socket socket contact
3 8

Resistance: max. 1.5 Ohm

- Eliminate open circuit in wiring/short circuit if necessary.

If none of the checks reveals a fault:
- Replace Motronic ECM power supply relay -J271-.