Inspection Procedure 2: The FCM cannot be turned on or off when the Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch is operated.


caution
  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C - Troubleshooting ).
  • When the hydraulic unit assembly (integrated with ASTC-ECU) is replaced, always carry out the calibration of the steering wheel sensor and the G sensor (Refer to ).
  • Before replacing the ECU, ensure that the communication circuit is normal.
  • When the FCM-ECU is replaced, calibrate the radar (refer to ).

COMMENTS ON TROUBLE SYMPTOM

  • The FCM-ECU has detected an abnormality.
  • The Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch circuit is short-circuited.
  • The FCM cannot be turned on under any of the conditions:

    1. Transfer position: 4LLc
    2. Rear differential lock: ON
    3. Hill descent control: ON
    4. ASC: OFF

PROBABLE CAUSES

  • Damaged wiring harness and connectors
  • Malfunction of Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch
  • Malfunction of ASTC-ECU
  • Malfunction of FCM-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 2.
Repair the CAN bus lines. (Refer to GROUP 54C - Troubleshooting .)

STEP 2. M.U.T.-III data list
Check the FCM system data list.

  • Press the Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch.
Item No.
 Item name
 Normal condition
20
 FCM switch state
 ON (the switch being pressed)

Q. Is the check result normal?
Go to Step 8.
Go to Step 3.

STEP 3. M.U.T.-III data list for other system
Check the ASTC system data list.

  • Press the Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch.
Item No.
 Item name
 Normal condition
32
 FCM off switch
 ON (the switch being pressed)

Q. Is the check result normal?
Go to Step 8.
Go to Step 4.

STEP 4. Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch check
Check the Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch (Refer to ).

Q. Is the check result normal?
Go to Step 5.
Replace the Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch.

STEP 5. Resistance measurement at Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch connector.
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Measure the resistance between the Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch connector (earth terminal) and the body earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?
Go to Step 7.
Go to Step 6.

STEP 6. Check of open circuit in earth line between Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch connector and the body earth

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.

STEP 7. Check of open circuit in FCSW line between ASTC-ECU connector and Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch connector

Q. Is the check result normal?
Replace the ASTC-ECU (Refer to ).
Repair the connector(s) or wiring harness.

STEP 8. Retest the system.
Check that the FCM control operates normally.

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunction ).
Replace the FCM-ECU (Refer to ).