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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 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 ON/OFF switch remains on for at least one minute.
 
 
TROUBLESHOOTING HINTS
  • Malfunction of the FCM 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.-III) other system data list.
(1)
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).
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) Check the ASC-ECU data list (Refer to ).
  • When the FCM ON/OFF switch is pressed.
 
Item No.Item nameNormal condition
167FCM ON/OFF switchON
Item No.Item nameNormal condition
167FCM ON/OFF switchON
  • When the FCM ON/OFF switch is not pressed.
 
Item No.Item nameNormal condition
167FCM ON/OFF switchOFF
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.-III) data list.
Check the input signal (Refer to ).
  • When the FCM ON/OFF switch is pressed.
 
Item No.Item nameNormal condition
25FCM ON/OFF switchON
Item No.Item nameNormal condition
25FCM ON/OFF switchON
  • When the FCM ON/OFF switch is not pressed.
 
Item No.Item nameNormal condition
25FCM ON/OFF switchOFF
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 the ignition switch from "LOCK" (OFF) position to "ON" position.
(3) 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 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 ON/OFF switch.
Refer to .
Is the check result normal?
Go to Step 6.
Replace the FCM ON/OFF switch (Refer to ).
 
STEP 6. Scan tool (M.U.T.-III) other system data list.
Check the ASC-ECU data list (Refer to ).
  • When the FCM ON/OFF switch is pressed.
 
Item No.Item nameNormal condition
167FCM ON/OFF switchON
Item No.Item nameNormal condition
167FCM ON/OFF switchON
  • When the FCM ON/OFF switch is not pressed.
 
Item No.Item nameNormal condition
167FCM ON/OFF switchOFF
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 ).