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Inspection procedure 24: Fuel pump system
 
 
 
 
CIRCUIT OPERATION
  • The fuel pump drive power is supplied from MFI relay to fuel pump relay (ETACS-ECU terminal F/PB) in the ETACS-ECU.
  • The battery positive voltage is applied by the ignition switch <Vehicles without KOS> or the OSS-ECU <Vehicles with KOS> to the fuel pump coil (ETACS-ECU terminal IG1) in the ETACS-ECU. The ECM turns "ON" the relay by turning "ON" the power transistor in the unit so as to conduct power to the fuel pump relay coil (via the ETACS-ECU terminal FP/R).
  • When the fuel pump relay is turned "ON", the battery positive voltage will be supplied from the fuel pump relay (ETACS-ECU terminal F/P) 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 stored 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 ETACS-ECU. Then confirm that the malfunction symptom is eliminated.
 
STEP 3. Measure the power supply voltage at ECM harness side connector.
(1) Disconnect the ECM connector and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal FP/R 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 4.
Repair or replace the connector(s), or check and repair the harness of short to ground and open circuit in FP/R line between ETACS-ECU connector and ECM connector. Then go to Step 6.
 
STEP 4. Measure the power supply voltage at ETACS-ECU connector.
(1) Disconnect the ETACS-ECU connector and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal F/PB 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.
Repair or replace the connector(s), or check and repair the harness of short to ground and open circuit in F/PB line between MFI relay connector and ETACS-ECU connector. Then confirm that the malfunction symptom is eliminated.
 
STEP 5. Check the fuel pump operation.
Refer to Fuel Tank pomp Operation Check .
Is the fuel pump operating properly?
Go to Step 6.
Replace the fuel pump module. Then confirm that the malfunction symptom is eliminated.
 
STEP 6. Check for continuity at fuel pump module 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 ground.
  • Continuity (2 ohms or less).
Does continuity exist?
Go to Step 7.
Repair or replace the connector(s), or check and repair the harness of open circuit and harness damage in ground line between fuel pump connector and ground. Then confirm that the malfunction symptom is eliminated.
 
STEP 7. Measure the power supply voltage at fuel pump module 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 F/P 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 11.
Go to Step 8.
 
STEP 8. Check of short to ground and open circuit in F/P line between ETACS-ECU connector and fuel pump module connector.
Is the harness wire in good condition?
Go to Step 9.
Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.
 
STEP 9. Check of harness damage in FP/R line between ETACS-ECU connector and ECM 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. 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 11. Check of harness damage in F/PB line between MFI relay connector and ETACS-ECU connector.
Is the harness wire in good condition?
Repair or replace the connector(s), or check and repair the harness of damage in F/P line between ETACS-ECU and fuel pump module connector. Then confirm that the malfunction symptom is eliminated.
Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.