Diagnosis Procedure

1. Turn the ignition switch OFF.
2. Disconnect 4WAS front control unit harness connector.
3. Check the voltage between 4WAS front control unit harness connector terminal and ground.

   4WAS front control unit		-	Voltage (Approx.)
   Connector	Terminal
   M41	11	Ground	Battery voltage

4. Turn the ignition switch ON.
   CAUTION: Never start the engine.
5. Check the voltage between 4WAS front control unit harness connector terminal and ground.

   4WAS front control unit		-	Voltage (Approx.)
   Connector	Terminal
   M41	11	Ground	Battery voltage

   Is the inspection result normal? 

   YES: GO TO  3.

   NO: GO TO 2.

1. Turn the ignition switch OFF.
2. Check the 40A fusible link (Q).
3. Check the harness for open or short between 4WAS front control unit harness connector No. 11 terminal and 40A fusible link (Q).

   Is the inspection result normal? 

   YES: Perform the trouble diagnosis for power supply circuit. Refer to "WIRING DIAGRAM - BATTERY POWER SUPPLY - ".

   NO: Repair or replace error-detected parts.

1. Turn the ignition switch OFF.
2. Disconnect 4WAS front control unit harness connector.
3. Check the voltage between 4WAS front control unit harness connector terminal and ground.

   4WAS front control unit		-	Voltage (Approx.)
   Connector	Terminal
   M42	15	Ground	0 V

4. Turn the ignition switch ON.
   CAUTION: Never start the engine.
5. Check the voltage between 4WAS front control unit harness connector terminal and ground.

   4WAS front control unit		-	Voltage (Approx.)
   Connector	Terminal
   M42	15	Ground	Battery voltage

   Is the inspection result normal? 

   YES: GO TO  5.

   NO: GO TO 4.

1. Turn the ignition switch OFF.
2. Check the 10A fuse (#3).
3. Disconnect fuse block (J/B) harness connector.
4. Check the continuity between 4WAS front control unit harness connector and fuse block (J/B).

   4WAS front control unit		Fuse block (J/B)		Continuity
   Connector	Terminal	Connector	Terminal
   M42	15	M1	2A	Existed

5. Check the continuity between 4WAS front control unit harness connector and the ground.

   4WAS front control unit		-	Continuity
   Connector	Terminal
   M42	15	Ground	Not existed

   Is the inspection result normal? 

   YES: Perform the trouble diagnosis for ignition power supply circuit. Refer to "WIRING DIAGRAM - IGNITION POWER SUPPLY - ".

   NO: Repair or replace error-detected parts.

Check the continuity between 4WAS front control unit harness connector terminal and the ground.

Is the inspection result normal? 

YES: GO TO 6.

NO: Repair or replace the harnesses and connectors.

Check 4WAS front control unit harness connector pin terminal and connection for disconnection.

Is the inspection result normal? 

YES: GO TO 7.

NO: Repair or replace the error-detected parts.

• Check that any item below is applicable when the malfunctions occur.
  • The engine stall occurs while driving or stopping the vehicle.
  • When detecting the charging system error

  Is the item applicable? 

  YES: Check the error system.

  • Perform ECM symptom diagnosis. Refer to "SYMPTOM TABLE " (VQ37VHR), "SYMPTOM TABLE " (VK56VD).
  • Perform the symptom diagnosis for the charging system. Refer to "SYMPTOM TABLE ".

  NO: Replace 4WAS front control unit. Refer to "REMOVAL AND INSTALLATION ".

  • Before replacing 4WAS front control unit, record the self-diagnosis results (history). Refer to "SPECIAL REPAIR REQUIREMENT ".