Inspection Procedure 30

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 case:
- Malfunction of the fuel pump relay.
- Malfunction of the fuel pump.
- Improper connector contact, open circuit or short-circuited harness wire.
- Malfunction of the ECM.
- Malfunction of the PCM.

WIRING DIAGRAM

CONNECTORS

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

CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.

STEP 1. Using scan tool MB991502, actuator test item 07: Fuel Pump.
- An operating sound of the fuel pump should be heard. If no sound is heard, go to Step 2.
If a sound is heard, this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points >.

STEP 2. Check the fuel pump operation.
1. Disconnect fuel pump connector D-14.
2. Use jumper wires to connect fuel pump connector terminal 5 to the 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-14.
1. Disconnect connector D-14 and measure at the harness side.
2. Check for the continuity between terminal 4 and ground.
- There should be continuity (0 Ohm). If continuity, go to Step 4.

STEP 4. Check the fuel pump relay.
1. Remove the fuel pump relay.
2. Check for the continuity between the fuel pump relay terminals 2 and 4
- There should be continuity (approximately 70 Ohm).
3. Use jumper wires 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 the fuel pump relay terminals 1 and 3 while connecting and disconnecting the jumper wire at the negative battery terminal.
- There should be continuity (0 Ohm) when the jumper wire is connected to the battery terminal, and there is no continuity when it is disconnected.
5. Install the fuel pump relay.
If all checks above meet the specifications, go to Step 5. If any check above does not meet the specifications, replace the fuel pump relay. Then confirm that the malfunction symptom is eliminated.

STEP 5. Check the power supply line at the fuel pump relay connector A-20X.
1. Disconnect connector A-20X and measure at the harness side.
2. Turn the ignition switch "ON."
3. Connect terminal 3 and ground, and terminal 4 and ground via a 20 Ohm resistor.
Measure the current at this time.
- The current should be 0.5 ampere or more.
4. Turn the ignition switch "OFF."
If within specifications, go to Step 6.
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 6. Check the circuit at ECM connector C-35 or PCM connector C-39 .
1. Disconnect connector C-35 or C-39 and measure at the harness side.
2. Turn the ignition switch "ON."
3. Connect the terminal 8 or 20 to ground via a 20 Ohm resistor. Measure current at this time.
- The current should be 0.14 amperes or more.
4. Turn the ignition switch off.
If within the specifications, go to Step 7.
If not within the specifications, repair the harness wire between ECM connector C-35 or PCM connector C-39 and the fuel pump relay connector A-20X. Then confirm that the malfunction symptom is eliminated.

STEP 7. Check the harness wire between fuel pump connector D-14 and ECM connector C-35 or PCM connector C-39 .

NOTE: Check the wire after checking intermediate connectors C-17 and C-19. If intermediate connectors C-17 and C-19 are damaged, repair or replace them. Refer to Harness Connector Inspection >. Then check that the malfunction is eliminated.

If the wire between fuel pump connector D-14 and ECM connector C-35 or PCM connector C-39 is not damaged, go to Step 8.
If the wire between fuel pump connector D-14 and ECM connector C-35 or PCM connector C-39 is damaged, repair it. Then confirm that the malfunction symptom is eliminated.

STEP 8. Check harness connector C-35 at the ECM or harness connector C-39 at the PCM for damage.
If harness connector C-35 or C-39 is damaged, repair or replace it. Refer to Harness Connector Inspection >.
If harness connector C-35 or C-39 is in good condition, replace the ECM or PCM.
Then confirm that the malfunction symptom is eliminated.