Code No.C1803 ACC mode off disagreement
Code No.C1804 ACC deactivation disagreement


caution Before replacing the ECU, ensure that the communication circuit is normal.

OPERATION
The ASC-ECU receives ACC control status signal from the ACC/FCM-ECU, and vehicle control status signal from the engine-ECU via CAN bus lines, respectively.

DIAGNOSIS CODE SET CONDITIONS
If the information received from the ACC/FCM-ECU does not correspond to that received from the engine-ECU, the ASC-ECU will store the diagnosis code.

PROBABLE CAUSES

  • Wiring harness or connector failure of CAN bus line
  • Malfunction of ACC/FCM-ECU
  • Malfunction of ASC-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 - CAN Bus Diagnostics Table ). On completion, go to Step 3.

STEP 2. M.U.T.-III Diagnosis code of other system
Use M.U.T.-III to check that the diagnosis code is set by the engine-ECU and ACC/FCM-ECU.

Q. Is the diagnosis code set?
Troubleshoot for the relevant diagnosis code. Refer to GROUP 13D - Troubleshooting <engine-ECU> or GROUP 17 - Adaptive Cruise Control System (ACC) <ACC/FCM-ECU>.
Go to Step 3.

STEP 3. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Ignition switch "LOCK" (OFF)
(3)Ignition switch "ON"

Q. Is diagnosis code No.C1803 or C1804 set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ). Then go to Step 4.
This diagnosis is complete.

STEP 4. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Ignition switch "LOCK" (OFF)
(3)Ignition switch "ON"

Q. Is diagnosis code No.C1803 or C1804 set?
Return to Step 1.
This diagnosis is complete.