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

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







Motronic Engine Control Module (ECM) Power Supply Relay -J271- is located in electronics box in plenum chamber, relay position 2.

NOTE:
- This test is only for vehicles up to m.y. 2004.
- Vehicles as of m.y. 2005, check Motronic Engine Control Module (ECM) Power Supply Relay -J271- according to wiring diagram.

- Disconnect voltage supply relay -2-.

Checking voltage supply







- Connect multimeter for voltage measurement as follows.

Relay carrier in E-box, plenum Measure to
chamber, position 2 Terminal
1 Engine Ground (GND)
2 Engine Ground (GND)
Specified value: approx. battery voltage

If specified value is not obtained:
- Repair open circuit in wiring or short circuit if necessary.

Checking activation







If specified value is not obtained:
- Connect portable multimeter for voltage measurement as follows.

Relay carrier in E-box, plenum Measure to
chamber, position 2 Terminal
4 B+

- Switch ignition on.
Specified value: approx. battery voltage
- Switch ignition off.

If specified value is not obtained:
- Connect V.A.G 1598/31 test box to wiring harness of Engine Control Module (ECM).







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

Relay carrier in E-box, plenum Measure to
chamber, position 2 Terminal
4 23

- Check the wire for short circuit to B+ and Ground (GND).
Specified value: Infinity Ohms (no continuity)
- Repair open circuit in wiring or short circuit if necessary.

If no malfunctions are detected:
- Replace Motronic Engine Control Module (ECM) Power Supply Relay -J271-.
- Read readiness code. If DTC memory was erased, readiness code must be generated again