Fuel Pump (FP) Relay -J17 and Relay Activation, Checking

Fuel Pump (FP) Relay -J17- and Relay Actuation, Checking

Voltage is supplied to the fuel pump and some injection system components via the Fuel Pump (FP) relay -J17-.
The condition for the closing of the fuel pump relay is that the engine should be turning. i.e. the relay is only connected to earth (via the engine control module) when engine speed pulses are detected in the engine control module.

Test conditions
- Battery voltage OK.

Functional testing of fuel pump relay

NOTE: Fuel pump relay is located in the micro central electrics underneath storage compartment on driver's side, relay position 4.







- Connect Vehicle Diagnostic, Testing and Information System VAS 5051 or V.A.G 1551 Scan Tool and select engine electronics control module with "Address word" 01. For this purpose, ignition must be switched on.
Connecting VAS 5051 Scan Tool
[1][2]Scan Tool Connecting and Initial Checks
- Start output Diagnostic Test Mode (DTM).
Output Diagnostic Test Mode (DTM) (Function 03)







Fuel pump relay should pick up and fuel pump should run

If the relay does not respond:

- Check actuation of fuel pump relay.

If the fuel pump does not run.

- Check actuation of fuel pump and components

Checking actuation of fuel pump relay

- Switch ignition off.
- Connect test box VAG 1598/31 to wiring harness for engine control module; do not connect engine control module. Connecting VAG 1598/31 Test Box
- Connect together sockets 65 and 2 on the test box using an auxiliary cable from VAG 1594.

Specified value: The fuel pump relay (relay position 4) must respond.

If the relay responds now, but not during output DTM:
- Replace engine control module.

If the relay does not respond:







- Remove fuel pump relay from relay base (relay position 4).







- Connect hand-held multimeter to contact 19 of relay socket and Ground to measure voltage.

Specified value: approx. battery voltage

If specified value is not attained:
- Check wiring connections.

If specified value is attained:







- Check for open circuit and short to positive or Ground in following wiring connection:

Test box V.A.G
1598/31 Socket Micro central electrics position 4 Contact

65 16

Wire resistance: max. 1.5 Ohm

- Correct any open/short circuit as necessary.

If no wiring malfunction is detected:

- Replace Fuel Pump relay -J17-.
- Read readiness code. If DTC memory was erased, re-generate readiness code. Readiness Code, Generating

Checking actuation of fuel pump and components

- Remove cover of fuses.







- Remove fuses 28, 29 and 34.
- Start output DTM. Output Diagnostic Test Mode (DTM) (Function 03)
- Connect hand-held multimeter (voltage measurement range) between Ground and either left or right contact of following fuses (only fuse contact is live).

Fuse No. Specified value at left or right Contact
28 approx. battery voltage
29 approx. battery voltage
34 approx. battery voltage

If the specified values are not obtained:

- Check wiring connections.

If no wiring malfunction is detected:

- Replace Fuel Pump (FP) relay -J17-.
- Re-insert all removed fuses.
- Read readiness code. If DTC memory was erased, re-generate readiness code. Readiness Code, Generating