Code No.C1784: FCM switch fixed ON


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.
  • Whenever the ECU is replaced, ensure that the CAN bus lines are normal.

OPERATION
The ACC/FCM-ECU receives the FCM ON/OFF switch signal from the ETACS-ECU via CAN communication.

DIAGNOSIS CODE SET CONDITION
This diagnosis code is set when the abnormality below is detected:

  • The FCM ON/OFF switch remains on for at least one minute.

PROBABLE CAUSES

  • Damaged harness wires and connectors
  • Malfunction of FCM ON/OFF switch
  • Malfunction of ETACS-ECU
  • Malfunction of ACC/FCM-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics.
Use M.U.T.-III to perform the CAN bus diagnosis.

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 for other system
Check the ETACS-ECU system data list.

  • FCM ON/OFF switch: OFF
Item No.
 Item name
 Normal condition
404
 FCM switch
 OFF

  • FCM ON/OFF switch: ON
Item No.
 Item name
 Normal condition
404
 FCM switch
 ON (the switch being pressed)

Q. Is the check result normal?
Go to Step 5
Go to Step 3

STEP 3. Check the FCM ON/OFF switch.
Refer to .

Q. Is the check result normal?
Go to Step 4
Replace the FCM ON/OFF switch.

STEP 4. Check of short circuit in FCMS line between ETACS-ECU connector and FCM ON/OFF switch connector

Q. Is the check result normal?
Replace the ETACS-ECU (Refer to GROUP 54A - ETACS-ECU ).
Repair the connector(s) or wiring harness.

STEP 5. M.U.T.-III data list.
Check the ACC/FCM system data list.

  • FCM ON/OFF switch: OFF
Item No.
 Item name
 Normal condition
52
 FCM switch state
 OFF

  • FCM ON/OFF switch: ON
Item No.
 Item name
 Normal condition
52
 FCM switch state
 ON (the switch being pressed)

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunction ).
Replace the ACC/FCM-ECU (Refer to GROUP 17 - Adaptive Cruise Control System (ACC) ).