Code No.C1784: FCM switch fixed ON
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- 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.
- When the FCM-ECU is replaced, calibrate the radar (refer to
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OPERATION
The FCM-ECU receives the FCM ON/OFF switch signal from the ASTC-ECU via CAN communication.
DIAGNOSIS CODE SET CONDITION
This diagnosis code is set when the abnormality below is detected:
- The Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch remains on for at least one minute.
PROBABLE CAUSES
- The CAN bus line is defective.
- Malfunction of the hydraulic unit assembly (integrated with ASTC-ECU)
- Damaged wiring harness and connectors
- Malfunction of Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch
- Malfunction of the FCM-ECU
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STEP 1. M.U.T.-III CAN bus diagnosis
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Use M.U.T.-III to diagnose the CAN bus lines.
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Q.
Is the check result normal?
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 Go to Step 2.
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 Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting ). On completion, go to Step 2.
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STEP 2. Use M.U.T.-III to confirm a diagnosis code of other systems.
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Check if the diagnosis code is set in the ASTC-ECU (Refer to Diagnosis Code Chart ).
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Q.
Is the diagnosis code set?
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Troubleshoot the ASTC-ECU diagnosis code (Refer to Diagnosis Code Chart ).
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Go to Step 3.
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STEP 3. Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch check
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Check the Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch (Refer to ).
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Q.
Is the check result normal?
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Go to Step 4.
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Replace the Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch.
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STEP 4. Check of short circuit in FCSW line between ASTC-ECU connector and Forward collision mitigation system (FCM) and Ultrasonic misacceleration Mitigation System ON/OFF switch connector
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Q.
Is the check result normal?
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Go to Step 5.
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Repair the connector(s) or wiring harness.
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STEP 5. Check whether the diagnosis code is set again.
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Check again if the diagnosis code is set in the FCM-ECU.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
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(4)On completion, check that the diagnosis code is set again.
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Q.
Is diagnosis code No. C1784 set?
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Replace the FCM-ECU (Refer to ).
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Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunctions ).
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