Checking Fuel Pump Relay/ Fuel Pump

Checking Fuel Pump Relay/ Fuel Pump


Fault System
Engine will not start.

Diagnostic Help
The output stage for activation of the fuel pump relay is monitored by the Motronic system. See Diagnostic trouble codes P1501, P1502, P1541.


Diagnostic Procedure






1 - Check the fuses
- Check that the following fuses are intact:
- MAXI fuse 2 (+30 circuit, main pump relay power supply).
- 32 (fuel pump relay power supply).

Are the fuses intact?

YES Continue to point 2.

NO Change the fuse and start the engine. If the fuse blows, continue with point 6.






2 - Check the performance of the fuel pump
- Forcibly actuate the fuel pump by connecting a jumper lead between fuses 4 and 32.
The fuel pump should start working.

Did the fuel pump start working?

YES Continue with point 3.

NO Continue with point 5.






3 - Check the current applied to the pump relay
- Remove the pump relay.
- Connect a test lamp to the relay socket between:
- pin 30 and a good ground.
The test lamp should light up.

Did the test lamp light up?

YES Continue with point 4.

NO Check and if necessary repair or replace the lead between pin 30 of the relay socket and crimped connection J93.






4 - Check the fuel pump relay
- Connect a jumper lead to the relay socket between:
- pins 30 and 87.
- Listen for the sound of the fuel pump working.

Is the fuel pump working?

YES Change the fuel pump relay.

NO Check and if necessary repair or replace the lead between pin 87 of the relay socket and fuse 32.






5 - Check the fuel pump
- Unplug the connector H2-9 from the fuel pump. The connector is located adjacent to the fuel pump under the rear seat. Note that the connector with the two thick cables is the right one. The other one is connected to the level sensor.
- Connect the test lamp to the 2-pin male connector between:
- pins 1 and 2.
- Connect an ISAT scan tool.
- Select "ACTIVATE".
- Select "FUEL PUMP RELAY".
The test lamp should flash at a frequency of 1 Hz.

Test Lamp Flashing?

YES Check and if necessary change the fuel pump or the wiring between H4-7 and H2-9.

NO First check and if necessary repair or replace the lead between pin 2 and grounding point G3. If this does not help, deal with the lead between pin 1 and fuse 32 in the same way.






6 - Check the fuel pump
- Unplug connector H2-9 from the fuel pump. The connector is located adjacent to the fuel pump under the rear seat.
- Change fuse 32.
- Connect an ISAT scan tool.
- Select "ACTIVATE".
- Select "FUEL PUMP RELAY".

Did the fuse blow?

YES Check and if necessary repair or replace the wiring harness between fuse 32 and pin 1 of connector H2-9.

NO Change the fuel pump.