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Inspection procedure 23: Fuel pump system
 
 
 
 
CIRCUIT OPERATION
  • The fuel pump drive power is supplied from MFI relay to fuel pump relay.
  • The battery positive voltage is applied by the ignition switch <Vehicles without KOS> or the IG1 relay <Vehicles with KOS> to the fuel pump relay coil. The ECM connector terminal FP/R turns "ON" the relay by turning "ON" the power transistor in the unit so as to conduct power to the fuel pump relay coil.
  • When the fuel pump relay is turned "ON", the battery positive voltage will be supplied from the fuel pump relay to the fuel pump.
 
 
COMMENT
  • When the ignition switch ON signal is inputted into the ECM, the ECM turns ON the fuel pump relay. This causes the battery voltage to be supplied to the fuel pump.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • Fuel pump relay failed.
  • Fuel pump failed.
  • Open or shorted fuel pump circuit, harness damage or connector damage.
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: Vehicles Communication Interface (V.C.I.)
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
STEP 1. Using scan tool (M.U.T.-III), check actuator test item 9: Fuel Pump.
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
(1) Connect scan tool (M.U.T.-III). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III) .
(2) Turn the ignition switch to the "ON" position.
(3) Set scan tool (M.U.T.-III) to the actuator test mode for item 9, Fuel Pump.
  • An operation sound of the fuel pump should be heard.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the fuel pump operating properly?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
Go to Step 2.
 
STEP 2. Check the fuel pump relay.
Refer to Fuel Pump Relay Continuity Check .
Is the fuel pump relay normal?
Go to Step 3.
Replace the fuel pump relay. Then confirm that the malfunction symptom is eliminated.
 
STEP 3. Measure the power supply voltage at ECM harness side connector.
(1) Disconnect the connector and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal FP/R line and ground.
  • Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 5.
Go to Step 4.
 
STEP 4. Check of open circuit and short circuit to ground in FP/R line between fuel pump relay connector and ECM connector.
Is the harness wire in good condition?
Repair or replace the connector(s), or check and repair the harness of open circuit and short circuit to ground in coil power supply line between J/B connector IG1 terminal and fuel pump relay connector. Then confirm that the malfunction symptom is eliminated.
Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.
 
STEP 5. Measure the power supply voltage at fuel pump relay harness side connector.
(1) Disconnect the fuel pump relay and measure at the J/B side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal switch side power supply line and ground.
  • Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 6.
Repair or replace the connector(s), or check and repair the harness of open circuit, and short circuit in power supply line between MFI relay connector and fuel pump relay connector. Then confirm that the malfunction symptom is eliminated.
 
STEP 6. Check the fuel pump operation.
Refer to Fuel Tank pomp Operation Check .
Is the fuel pump operating properly?
Go to Step 7.
Replace the fuel pump module. Then confirm that the malfunction symptom is eliminated.
 
STEP 7. Check the continuity at fuel pump harness side connector.
(1) Disconnect the fuel pump module connector and measure at the harness side.
(2) Check for the continuity between terminal ground line and body ground.
  • Continuity (2 ohms or less).
Does continuity exist?
Go to Step 8.
Repair or replace the connector(s), or check and repair the harness of open circuit and damage in ground line between fuel pump module connector and body ground. Then confirm that the malfunction symptom is eliminated.
 
STEP 8. Measure the power supply voltage at fuel pump harness side connector.
(1) Disconnect the fuel pump module connector and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal power supply line and ground.
  • Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 12.
Go to Step 9.
 
STEP 9. Check of open circuit and short circuit to ground in power supply line between fuel pump relay connector and fuel pump module connector.
Is the harness wire in good condition?
Go to Step 10.
Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.
 
STEP 10. Check of harness damage in FP/R line between fuel pump relay connector and ECM connector.
Is the harness wire in good condition?
Go to Step 11.
Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.
 
STEP 11. Using scan tool (M.U.T.-III), check actuator test item 9: Fuel Pump.
(1) Turn the ignition switch to the "ON" position.
(2) Set scan tool (M.U.T.-III) to the actuator test mode for item 9, Fuel Pump.
  • An operation sound of the fuel pump should be heard.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Is the fuel pump operating properly?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
Replace the ECM (Refer to, Removal and Installation ). Then confirm that the malfunction symptom is eliminated.
 
STEP 12. Check of harness damage between MFI relay connector and fuel pump relay connector.
Is the harness wire in good condition?
Repair or replace the connector(s), or check and repair the harness of damage in switch side power supply line between MFI relay connector and fuel pump relay connector. Then confirm that the malfunction symptom is eliminated.
Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.