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

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

Special tools and equipment






- VAG1526A
- VAG1594A
- VAG1598/31

NOTE: The Motronic Engine Control Module (ECM) power supply relay -J271- supplies voltage to the ignition coils with power output stages and the Engine Control Module (ECM) at pin 121.

Test sequence






- Disconnect the 4-pin harness connector -1- at one of the ignition coils -2-.






- Connect multimeter for voltage measurement as follows.

Harness connector Measure to
Terminal
1 Engine Ground (GND)

- Switch ignition on.
- Specification: approx. battery voltage

If specified value is not obtained:






- Disconnect voltage supply relay -2- below left cover at bulkhead.

NOTE: To remove the protective hood for the TT Roadster relay carrier, disengage at the bulkhead and swing downward. Disconnect additional harness connectors at Mass Air Flow (MAF) sensor, if necessary.






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

Right relay carrier under cover at Harness connector at ignition
bulkhead coils
Terminal Terminal
2 1

- Repair open circuit if necessary.

If wire connection is OK:
- Check voltage supply of Motronic Engine Control Module (ECM) power supply relay -J271-.
- Check activation of Motronic Engine Control Module (ECM) power supply relay -J271-.

Checking voltage supply
- Switch ignition off.






- Disconnect voltage supply relay -2- below left cover at bulkhead.






- Connect multimeter for voltage measurement as follows.

Right relay carrier under cover Measure to
at bulkhead
Terminal
3 Engine Ground (GND)
1 Engine Ground (GND)

- Specification: approx. battery voltage

If specified value is not obtained:
- Perform the following tests marked with dots:






- Check fuse S10 (in fuse holder, position 10).






- Check fuse S134 (110 A) in main fuse box/battery.
- Check wire connection from B+ (terminal 30) via fuse S134 and fuse 10 for voltage supply of Motronic Engine Control Module (ECM) power supply relay -J271- (below left cover, at bulkhead) for open circuit.

Checking activation
- Switch ignition off.






- Disconnect voltage supply relay -2- below left cover at bulkhead.






- Connect multimeter for voltage measurement as follows.

Right relay carrier under cover Measure to
at bulkhead
Terminal
5 B+

- Switch ignition on.
- Specification: approx. battery voltage

If specified value is not obtained:
- Switch ignition off.
- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. Wiring and Component Testing Using VAG1598/31 Test Box






- Check the following wire connection for open circuit and short circuit to Ground (GND) and B+:

Right relay carrier under cover VAG1598/31 test box
at bulkhead
Terminal Socket
5 21

- Repair open circuit or short circuit if necessary.

If no malfunctions are detected:
- Replace Motronic Engine Control Module (ECM) power supply relay -J271-.