Fuel Pump Relay: Testing and Inspection

Checking function

Note:
The fuel pump relay is located in the fuse/relay panel, on the left side under the instrument panel.

- Remove shelf in left front footwell.
- Remove lower right A-pillar trim.
- Fold back carpet in right front footwell.
- Remove cover from electronics box.

Central Electronics Box:

- Remove HO2S circuit breaker -2- (-S73- in brown holder) and injector valve circuit breaker -3- (-S72- in red holder).
- Remove fuse 17 from fuse holder.
- Connect US 1115 LED tester or equivalent between Ground (GND) and one terminal for fuse 17, using adapter cables from VW 1594 connector test kit.
- Operate starter briefly.
^ Fuel pump relay must be activated (can be felt and heard)
^ LED tester must light up

If fuel pump relay is NOT activated:
- Check activation of fuel pump relay.

If LED tester does NOT light up:
- Repeat test on other terminal for fuse 17.

If LED tester still does NOT light up:

Central Electric Panel With Detail Of Relay Position 6:

- Check wiring connection for continuity between fuse 17 and terminal 30 at relay position 6 per wiring diagram.
- Repair open circuit in wiring, if necessary.

Fuse Holder:

- Connect LED tester between GND and to terminal 1 of holder for injector valve circuit breaker -S72- (red holder).
- Use On-Board Diagnostics (OBD) output diagnostic test mode to activate fuel pump relay.
^ Fuel pump relay must be activated
^ LED tester must light up

If LED tester does not light up:
- Repeat test on circuit breaker holder terminal 2.

If LED tester does not light up:

Central Electric Panel With Detail Of Relay Position 6:

- Check wiring connection from circuit breaker to terminal 30 on relay location 6 for continuity per wiring diagram. Repair open circuit in wiring if necessary.

Fuse Holder:

- Connect LED tester between GND and to terminal 1 of holder for HO2S circuit breaker -S73- (brown holder).
- Use On-Board Diagnostics (OBD) output diagnostic test mode to activate fuel pump relay.
^ Fuel pump relay must be activated
^ LED tester must light up

If LED tester does not light up:
- Repeat test on circuit breaker holder terminal 2.

If LED tester does not light up again:
- Check wiring for continuity from circuit breaker holder and terminal 31 at relay position 6, according to wiring diagram.
- Repair open circuit in wiring if necessary.

Checking battery positive voltage (B+) for fuel pump relay

- Switch ignition on.

Central Electric Panel With Detail Of Relay Position 6:

- Connect multimeter (Fluke 83 or equivalent) to measure voltage at fuel pump relay panel sockets:
^ Sockets 28 (positive) and 34
^ Sockets 32 (B+) and 34 Specified value: approx. 12 volts
- Switch ignition off.

If the specified values are not obtained:
- Eliminate open circuits in wiring using wiring diagram.

Checking activation of fuel pump relay

- Connect US 1115 LED tester or equivalent to relay sockets 28 and 29.
^ Ignition on: LED must light up brightly for approx. 1 sec., then stay dimly lit
^ Starter operated: LED must become visibly brighter

If LED lights up dimly when ignition is switched on but does not get brighter when starter is operated:
- Replace Engine Control Module (ECM).

If LED tester does not light up, check wiring as follows:
- Connect VAG 1598 test box to ECM wiring harness using VAG 1598/12 adaptor harness. The numbers of the connectors are identical to those on the test box.
- Connect multimeter (Fluke 83 or equivalent) between relay socket 29 and test box socket 15 and check for open circuit.
Specified reading: maximum 1 (ohm)

If specified reading is not obtained:
- Eliminate open circuit in wiring using wiring diagram. If there is no open circuit and LED tester does not light up:
- Replace ECM.

If activation of fuel pump relay and wiring are both OK:
- Replace fuel pump relay -J17-.
- Replace fuse no. 17 and both circuit breakers again.