Inspection Procedure 30

Fuel Pump Circuit:

Connectors: C-51 <M/T>, C-52 <A/T>, C-92, D-17:

CIRCUIT OPERATION
- A battery positive voltage is applied on the fuel pump relay (terminal 3, 4) from the ignition switch-IG.
- During cranking and while the engine is running, the ECM or PCM turns the power transistor in the ECM or PCM ON to ground the fuel pump relay coil. With this, the fuel pump relay turns ON, and the battery positive voltage is supplied to the fuel pump from the fuel pump relay (terminal 1).

TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Malfunction of the fuel pump relay.
- Malfunction of the fuel pump.
- Improper connector contact, open or short-circuited harness wire.
- Malfunction of the ECM.
- Malfunction of the PCM.

DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.

STEP 1. Using scan tool MB991502, actuator test item 07: Fuel Pump.
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to ON" position.
3. Set scan tool MB991502 to the actuator test mode for item 07, Fuel Pump.
- An operating sound of the fuel pump should be heard.

If a sound is heard, this malfunction is intermittent.
Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope With Intermittent Malfunction.

If no sound is heard, go to Step 2.

STEP 2. Check the fuel pump operation.
1. Disconnect fuel pump connector D-17.
2. Use jumper wires to connect fuel pump connector terminal 5 to positive battery terminal, and terminal 4 to the negative battery terminal.
- An operating sound of the fuel pump should be heard.

If a sound is heard, go to Step 3.

If no sound is heard, replace the fuel pump. Then confirm that the malfunction symptom is eliminated.

STEP 3. Check the ground line at fuel pump connector D-17.
1. Disconnect connector D-17 and measure at the harness side.
2. Check for the continuity between terminal 4 and ground.
- Should be less than 2 ohms . If less than 2 ohms , go to Step 4.

If open circuit, repair the wire between the fuel pump connector D-17 and ground.
Then confirm that malfunction symptom is eliminated.

STEP 4. Check harness connector D-17 at the fuel pump for damage.
If harness connector C-17 is good condition, go to Step 5.

If harness connector C-17 is damaged, repair or replace it.
Refer to Harness Connector Inspection.
Then confirm that the malfunction symptom is eliminated.

STEP 5. Check the fuel pump relay.
1. Remove the fuel pump relay.

2. Check for the continuity between fuel pump relay terminals 2 and 4.
- There should be continuity (approximately 70 ohms).

3. Use a jumper wire to connect fuel pump relay terminal 4 to the positive battery terminal and terminal 2 to the negative battery terminal.
4. Check the continuity between fuel pump relay terminals 1 and 3 while connecting and disconnecting the jumper wire at the negative battery terminal.
- Should be less than 2 ohms . (Negative battery terminal connected)
- Should be open circuit. (Negative battery terminal disconnected)

5. Install the fuel pump relay.

If all checks above meet the specifications, go to Step 6. If any check above does not meet the specifications, replace the fuel pump relay.
Then confirm that the malfunction symptom eliminated.

STEP 6. Check the power supply line at fuel pump relay connector A-20X.
1. Disconnect connector A-20X and measure at the harness side.
2. Turn the ignition switch to "ON" position.
3. Measure voltage between terminal 3 and ground, and terminal 4 and ground.
- Voltage should be battery positive voltage.

4. Turn the ignition switch to "LOCK" (OFF) position. If within the specifications, go to Step 7.

If not within specifications, repair the harness wire between the fuel pump relay and the ignition switch.
Then confirm that the malfunction symptom is eliminated.

STEP 7. Check harness connector A-20X at the fuel pump relay for damage.
If harness connector A-20X is good condition, go to Step 8.

If harness connector A-20X is damaged, repair or replace it.
Refer to Harness Connector Inspection.
Then confirm that the malfunction symptom is eliminated.

STEP 8. Check the harness wire between fuel pump relay connector A-20X and fuel pump connector D-17.

NOTE: Check the wire after checking intermediate connectors C-28 and C-92. If intermediate connectors C-28 and C-92 are damaged, repair or replace them.
Refer to Harness Connector Inspection.
Then check that the malfunction is eliminated.

If the wire between fuel pump relay connector A-20X and fuel pump connector D-17 is in good condition, go to Step 9.

If the wire between fuel pump relay connector A-20X and fuel pump connector D-17 is damaged, repair it. Then confirm that the malfunction symptom is eliminated.

STEP 9. Check harness connector C-51 at the ECM or harness connector C-52 at the PCM for damaged.
If harness connector C-51 or C-52 is good condition, go to Step 10.

If harness connector C-51 or C-52 is damaged, repair or replace it.
Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.

STEP 10. Check the circuit at ECM connector C-51 or PCM connector C-52 .
1. Disconnect connector C-51 or C-52 and measure at the harness side.
2. Turn the ignition switch to "ON" position.
3. Measure voltage between terminal 21 and ground.
- Voltage should be battery positive voltage.

4. Turn the ignition switch to "LOCK" (OFF) position. If within specifications, replace the ECM or PCM. If not within specifications, repair the harness wire between fuel pump relay connector A-20X and ECM connector C-51 or PCM connector C-52 .
Then confirm that the malfunction symptom is eliminated.