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DTC C1784 FCM switch fixed ON
 
 
caution
  • Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
 
 
OPERATION
The FCM/LDW/AHB-ECU receives the FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch signal from the ASC-ECU via CAN communication.
 
 
DTC SET CONDITION
This DTC is set when the abnormality below is detected:
  • The FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch remains on for at least one minute.
 
 
TROUBLESHOOTING HINTS
  • Malfunction of the FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch (Stuck on)
  • Malfunction of the ASC-ECU
  • Malfunction of the FCM/LDW/AHB-ECU
  • Damaged harness wires and connectors
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Scan tool (M.U.T.-IIISE) other system data list.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the Scan Tool (M.U.T.-IIISE) ."
(2) Turn on the power supply mode of the electric motor switch.
(3) Check the ASC-ECU data list (Refer to ).
  • When the FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch is pressed.
 
Item No.Item nameNormal condition
167FCM ON/OFF switchON
  • When the FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch is not pressed.
 
Item No.Item nameNormal condition
167FCM ON/OFF switchOFF
OK: Normal condition is displayed.
Is the check result normal?
Go to Step 2.
Go to Step 4.
 
STEP 2. Scan tool (M.U.T.-IIISE) data list.
Check the input signal (Refer to ).
  • When the FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch is pressed.
 
Item No.Item nameNormal condition
25FCM ON/OFF switchON
  • When the FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch is not pressed.
 
Item No.Item nameNormal condition
25FCM ON/OFF switchOFF
OK: Normal condition is displayed.
Is the check result normal?
Go to Step 3.
Replace the FCM/LDW/AHB-ECU (Refer to ).
 
STEP 3. Check whether the DTC is set again.
Check again if the DTC is set in the FCM/LDW/AHB-ECU.
(1) Erase the DTC.
(2) Turn off the power supply mode of the electric motor switch.
(3) Turn on the power supply mode of the electric motor switch.
(4) Check if DTC is set.
Is the DTC set?
Replace the FCM/LDW/AHB-ECU (Refer to ).
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
 
STEP 4. Check of short to ground circuit in FCSW line between ASC-ECU connector and FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch connector.
Is the check result normal?
Go to Step 5.
Repair the connector(s) or wiring harness.
 
STEP 5. Check the FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch.
Refer to .
Is the check result normal?
Go to Step 6.
Replace the FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch (Refer to ).
 
STEP 6. Scan tool (M.U.T.-IIISE) other system data list.
Check the ASC-ECU data list (Refer to ).
  • When the FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch is pressed.
 
Item No.Item nameNormal condition
167FCM ON/OFF switchON
  • When the FCM and Ultrasonic misacceleration Mitigation System ON/OFF switch is not pressed.
 
Item No.Item nameNormal condition
167FCM ON/OFF switchOFF
OK: Normal condition is displayed.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ).