Fuel Pump Control Unit: Testing and Inspection

Fuel Pump (FP) Control Module J538 , Checking (vehicles With 4-cyl. TFSI Engine)







Special tools, testers and auxiliary items required
- Portable multimeter V.A.G 1526 B
- Connector test set V.A.G 1594 C
- Adapter cable V.A.G 1598/39
- Test box V.A.G 1598/42

Test conditions
- Battery voltage at least 12.5 V.







- Fuse on fuse panel S228 (position 28) OK.
- Ignition switched off.

Check voltage supply for Fuel Pump (FP) (from Fuel Pump (FP) Control Module J538 )
- Remove rear seat bench.







- Unbolt cover for right locking flange - arrows - .
- Fold protective boot back.







- For voltage testing, connect the hand multimeter V.A.G 1526 B with measuring probes and connector adapters from the connector test set V.A.G 1594 C or V.A.G 1594 A between clamp - 1 - and - 4 - , as shown in illustration. The electrical connection remains connected.

NOTE: Connector sockets are numbered respectively on the rear side of the connector.

- Start engine.
- Specified value during start and while running at idle: 4 to 5.7 V.
- Depress accelerator pedal completely and then release it (brief throttle burst).
- Specification: The voltage value must first rise slightly, then fall and then rise again to the previously read value.

If the reading does not result as described:
- Check voltage supply and activation of Fuel Pump (FP) Control Module J538.

Check voltage supply for Fuel Pump (FP) Control Module J538
- Remove Fuel Pump (FP) Control Module J538.







- Disconnect electrical harness connector - arrow - on Fuel Pump (FP) Control Module J538 .







- Connect multimeter between terminal - 3 - and - 4 - of harness connector for voltage measurement.
- Switch ignition on.
- Specification: approx. battery voltage.

If specification is not obtained:
- Repair open circuit in wiring according to wiring diagram.

Check activation of Fuel Pump (FP) Control Module J538
- Remove protective cap.







- For voltage testing, connect the multimeter with measuring probes and connector adapters from the connector test set V.A.G 1594 C between clamp - 4 - and - 5 - , as shown in illustration. The electrical connection remains connected.

NOTE: Connector sockets are numbered respectively on the rear side of the connector.

- Start engine.
- Specified value during start and while running at idle: approx. 5.0 V.
- Depress accelerator pedal completely and then release it (brief throttle burst).
- Specification: The voltage value must first rise slightly, then fall and then rise again to the previously read value.

If the reading does not result as described:
- Switch off ignition.







- Connect test box V.A.G 1598/42 to wiring harness with adapter cable V.A.G 1598/39-1 or adapter cable V.A.G 1598/39-2 ; engine control module (ECM) remains connected. Clamp test box Ground (GND) clip to battery negative terminal.

CAUTION: To avoid damaging electronic components, set measuring range before connecting test leads and observe all test requirements.







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

Harness connector Terminal Test box V.A.G 1598/42 Socket
- 5 - B 27

- Repair wiring open circuit or short circuit according to wiring diagram.

If no malfunctions are detected:
- Replace Fuel Pump (FP) Control Module J538.