Inspection Procedure 29
Fuel Pump Circuit:
Connectors:
CIRCUIT OPERATION
- If the ignition switch is turned "ON", the fuel pump relay operates. This causes positive battery positive voltage to be supplied from the fuel pump relay (terminal 1) to the fuel pump relay module (terminal 1).
- The PCM sends the pump drive signal to the fuel pump relay module (terminal 2). The pump drive signal depends on the engine speed (Low, Middle, or High).
- The fuel pump relay module (terminal 3) activates the fuel pump in accordance with the pump drive signal.
TECHNICAL DESCRIPTION
- The PCM detects the engine speed (Low, Middle or High), and sends the fuel pump drive signal to the fuel pump relay module in accordance with that engine speed. Based on this signal, the fuel pump relay module controls the fuel pump.
- When the engine r/min is high, the fuel pump operates at high speed, and when the engine r/min is low, the fuel pump operates at low speed.
TROUBLESHOOTING HINTS
The most likely causes for this case:
- Malfunction of the fuel pump relay.
- Malfunction of the fuel pump.
- Malfunction of the fuel pump relay module.
- Improper connector contact, open circuit or short-circuited harness wire.
- Malfunction of the PCM.
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, it can be assumed that this malfunction is intermittent. Refer to vehicle level Testing and Inspection.
STEP 2. Check the fuel pump operation
1. Disconnect the fuel pump relay module connector C-61.
2. Use jumper wires to connect the positive battery terminal to the fuel pump relay module harness side connector terminal 3, and the negative battery terminal to terminal 4, respectively.
- Fuel pump should operate.
If the fuel pump does not operate, go to Step 3.
If the fuel pump operates, go to Step 5.
STEP 3. Check the harness wire between the fuel pump relay module C-61 and the fuel pump connector E-26.
NOTE: After inspecting the intermediate connectors C-16 and E-44, inspect the wire. If the intermediate connectors C-16 and E-44 are damaged, repair or replace them. Refer to vehicle level Testing and Inspection. Then confirm that the malfunction symptom is eliminated.
If the wire between the fuel pump relay module connector C-61 and the fuel pump connector E-26 is not damaged, go to Step 4.
If the wire between the fuel pump relay module connector C-61 and the fuel pump connector E-26 is damaged, repair it.
Then confirm that the malfunction symptom is eliminated.
STEP 4. Check harness connector E-26 at the fuel pump for damage.
If harness connector E-26 is damaged, repair or replace it. Refer to vehicle level Testing and Inspection.
If harness connector E-26 is in good condition, replace the fuel pump.
Then check that the malfunction is eliminated.
STEP 5. 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 ohms).
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 ohms) 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 6. If any check above does not meet the specifications, replace the fuel pump relay. Then confirm that the malfunction symptom is eliminated.
STEP 6. Check the power supply line at the fuel pump relay connector C-60.
1. Disconnect connector C-60 and measure at the harness side.
2. Turn the ignition switch "ON".
3. Connect terminal 3 and the ground, and terminal 4 and the ground via a 20-ohms 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 7.
If not within specifications, repair the harness wire and connector between the fuel pump relay and the ignition switch. Refer to vehicle level Testing and Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 7. Check the power supply line at fuel pump relay module connector C-61.
1. Disconnect connector C-61 and measure at the harness side.
2. Turn the ignition switch "ON".
3. Connect terminal 1 to ground via a 20-ohms resistor to measure the current.
- Current should be 0.5 ampere or more.
4. Turn the ignition switch "OFF".
If less than 0.5 ampere, go to Step 8.
If 0.5 ampere or more, go to Step 9.
STEP 8. Check the harness wire between fuel pump relay connector C-60 and fuel pump relay module connector C-61.
If any harness wire between fuel pump relay connector C-60 and fuel pump relay module connector C-61 is damaged, repair it.
If no harness wire between fuel pump relay connector C-60 and fuel pump relay module connector C-61 is damaged, repair or replace the fuel pump relay connector C-60. Refer to vehicle level Testing and Inspection.
Then check that the malfunction is eliminated.
STEP 9. Check the ground line at the fuel pump relay module connector C-61.
1. Disconnect connector C-61 and measure at the harness side.
2. Check for the continuity between terminal 5 and ground.
- There should be continuity (0 ohms).
If continuity, go to Step 10.
If no continuity, repair the harness wire between fuel pump module connector C-61 and ground. Then check that the malfunction is eliminated.
STEP 10. Check the fuel pump drive signal line at fuel pump relay module connector C-61.
1. Disconnect connector C-61 and measure at the harness side.
2. Crank the engine.
3. Measure the voltage between terminal 2 and ground.
- Voltage should be between 0.7 and 2.8 volts.
4. Turn the ignition switch "OFF".
If not within the specification, go to Step 11.
If within the specification, go to Step 13.
STEP 11. Check the harness wire between fuel pump relay module connector C-61 and PCM connector C-89.
If no harness wire between fuel pump relay module connector C-61 and PCM connector C-89 is damaged, go to Step 12.
If any harness wire between fuel pump relay module connector C-61 and PCM connector C-89 is damaged, repair it. Then check that the malfunction is eliminated.
STEP 12. Check harness connector C-89 at the PCM for damage.
If harness connector C-89 is damaged, repair or replace it.
Refer to vehicle level Testing and Inspection.
If harness connector C-89 is in good condition, replace the PCM.
Then confirm that the malfunction symptom is eliminated.
STEP 13. Check harness connector C-61 at the fuel pump relay module for damage.
If harness connector C-61 is damaged, repair or replace it.
Refer to vehicle level Testing and Inspection.
If harness connector C-61 is in good condition, replace the fuel pump relay module.
Then check that the malfunction is eliminated.