Code No. C1804:
ACC Deactivation Disagreement <Vehicles with ACC/FCM>
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Before replacing the ECU,
ensure that the communication circuit is normal.
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OPERATION
The ASTC-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 ASTC-ECU will store the diagnosis code.
PROBABLE CAUSES
- Wiring harness or connector failure of CAN bus line
- Malfunction of engine-ECU
- Malfunction of ACC/FCM-ECU
- Malfunction of ASTC-ECU
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STEP 1. M.U.T.-III Diagnosis code.
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Use M.U.T.-III to check that the any diagnosis code other than C1804 is set in the ASTC-ECU.
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Q.
Is the any diagnosis code other than C1804 set?
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 Troubleshoot for the relevant diagnosis code.
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 Go to Step 2.
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STEP 2. M.U.T.-III Diagnosis code of other system.
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Use M.U.T.-III to check that the diagnosis code No. C1777 is set in the ACC/FCM-ECU.
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Q.
Is the diagnosis code No. C1777 set?
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Troubleshoot for the relevant diagnosis code {Refer to GROUP 17 - Adaptive
Cruise Control System (ACC), Troubleshooting, Diagnosis Code Procedures: Code No. C1777  }.
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Go to Step 3.
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STEP 3. Check whether the diagnosis code is set again.
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(1)Use the M.U.T.-III, erase the diagnosis code.
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(2)Turn the ignition switch to the "LOCK" (OFF) position.
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(3)Turn the ignition switch to the "ON" position.
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(4)Press the ACC ON/OFF switch to turn the ACC to ON.
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Q.
Is diagnosis code No. C1804 set?
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Replace the ACC/FCM-ECU {Refer to GROUP 17 - Adaptive Cruise
Control System (ACC), ACC/FCM-ECU }. Then go to Step
4.
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This diagnosis is complete.
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STEP 4. Check whether the diagnosis code is set again.
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(1)Use the M.U.T.-III, erase the diagnosis code.
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(2)Turn the ignition switch to the "LOCK" (OFF) position.
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(3)Turn the ignition switch to the "ON" position.
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(4)Press the ACC ON/OFF switch to turn the ACC to ON.
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Q.
Is diagnosis code No. C1804 set?
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Replace the hydraulic unit (integrated with ASTC-ECU).
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This diagnosis is complete.
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