WIS Document: 4027

| | Fuel pump relay Fault symptom Fuel pump relay not working Diagnostic procedure 1 Check the engine management system's power supply | - | Unplug connector H33-1. | - | Connect the test lamp to pin 30 of connector H33-1 and a good grounding point. | - | Turn the ignition switch to the "ST" position (+50). The test lamp should flash during starter motor cranking. Is the test lamp flashing? | yes Continue with point 2. | no Continue with point 4. 2 Check the wiring between connectors H33-1 and H33-4 Check the wiring harness for continuity between pin 30 of connector H33-1 and pin 11 of connector H33-4. The resistance should be < 1 ohm. Is the resistance correct? | yes Continue with point 3. | no Repair or replace the wiring harness. 3 Check the wiring connected to the engine management system Conduct a continuity test on the cable assembly between connector H33-4, pin 11 and | - | Trionic control module, pin 56. | - | Motronic 2.10.3 control module, pin 3 | - | Motronic 2.8.1 control module, pin 3 depending on the engine alternative. The resistance should be < 1 Ohm. Is the resistance correct? | yes Continue fault diagnosis as described in Service Manual 2:7 "Engine management system TRIONIC", "MOTRONIC 2.10.3" or "MOTRONIC 2.8.1". | no Repair or replace the wiring harness. 4 Check the operation of the fuel pump relay | - | Plug in connectors H33-1 and H33-4. | - | Unplug the fuel pump relay. | - | Connect the test lamp to pins 86 and 85 of the fuel pump relay socket. | - | Turn the ignition switch to the "ST" position (+50). The test lamp should flash during starter motor cranking. Is the test lamp flashing? | yes Continue fault diagnosis as described in Service Manual 2:7 "Engine management system "TRIONIC", "MOTRONIC 2.10.3" or "MOTRONIC 2.8.1". | no Continue with point 5. 5 Check the operation of the fuel pump relay (contd.) | - | Connect the test lamp to pins 85 and 30 of the fuel pump relay socket. | - | Turn the ignition switch to the "ST" position (+50). The test lamp should flash during starter motor cranking. Is the test lamp flashing? | yes Continue fault diagnosis as described in Service Manual 2:7 "Engine management system "TRIONIC", "MOTRONIC 2.10.3" or "MOTRONIC 2.8.1". | no Continue with point 6. 6 Check the wiring Check the wiring harness for continuity between pin 85 of the fuel pump relay socket and pin 29 of connector H33-3. The resistance should be < 1 ohm. Is the resistance correct? | yes Continue with point 7. | no Repair or replace the wiring harness. 7 Check the wiring connected to the electronic control module | - | Unplug the control module. | - | Check the wiring harness for continuity between - connector H33-1 (pin 30) and the electronic control module (pin 21). - connector H33-3 (pin 29) and the electronic control module (pin 9). The resistance should be < 1 ohm. Is the resistance correct? | yes Continue with point 8. | no Repair or replace the wiring harness. 8 Final check Start the car and check to see if the fault symptom remains. Is the problem still present? | yes See "Before replacing a control module". | no The remedial measures taken were correct or the fault is of intermittent nature.