Main Relay (Computer/Fuel System): Testing and Inspection

Motronic ECM Power Supply Relay, Checking

The Motronic ECM power supply relay -J271- is located in the electronics box (E-box) in the plenum.
See Electrical Wiring Diagrams, Troubleshooting and Component Locations.

The relay supplies power to the following components:
- Fuel injectors
- Motronic Engine Control Module (ECM) -J220-
- EVAP canister purge regulator valve -N80-
- Intake manifold change-over valve -N156-
- Air control valve for fuel injectors -N212-

Checking
- Remove Motronic ECM power supply relay -J271- from relay position 1 (E-box in plenum).







- Connect VAG 1527 LED voltage tester between relay socket terminal 2 (B+, terminal 30) and engine Ground.
- Connect VAG 1527 LED voltage tester between relay socket terminal 4 (B+, terminal 30) and engine Ground.
LED must light up both times.

If LED does not light;
- Check wiring for open circuits.
See Electrical Wiring Diagrams, Troubleshooting and Component Locations.







- Connect VAG 1527 LED voltage tester between relay socket terminals 2 (B+, terminal 30) and 6 (Ground for ECM).
- Switch ignition on.
LED must light up.

If LED does not light:
- Switch ignition off.
- Connect VAG 1598/19 test box to ECM harness connector. Testing and Inspection







- Check wiring for open circuits between relay socket terminal 6 and ECM/test box socket A2.
See Electrical Wiring Diagrams, Troubleshooting and Component Locations.

If there are no open circuits and LED still does not light up:
- Replace ECM and generate new readiness code. Testing and Inspection
- Reinstall Motronic ECM power supply relay.
- Disconnect test box and reconnect ECM.
- Switch ignition on.
- Connect VAG 1527 LED voltage tester between engine Ground and upper fuse terminal (fuses for fuel injectors and for EVAP canister purge regulator valve -N80-).
LED must light up (both fuses supply voltage to one terminal).

If LED does not light for either fuse:





- Check wiring for open circuit between fuses and Motronic ECM power supply relay socket terminal 8.
See Electrical Wiring Diagrams, Troubleshooting and Component Locations.

If there are no open circuits:
- Replace Motronic ECM power supply relay -J271-.
- Reinstall fuses and relay.
- Check readiness code See page 01-47. If DTC memory has been erased, generate new readiness code. Testing and Inspection