Code No. U1204: Steering wheel sensor communication error


caution
  • If diagnosis code No.U1204 is set in the ASTC-ECU, always diagnose the CAN main bus line. If there is any fault in the CAN bus lines, an incorrect diagnosis code may be set.
  • Whenever the ECU is replaced, ensure that the communication circuit is normal.

OPERATION


The steering wheel sensor detects a steering wheel angle and sends it to ASTC-ECU via the CAN bus line.

DIAGNOSIS CODE SET CONDITION


This diagnosis code is set when the ASTC-ECU power supply voltage is normal but the signal sent from the steering wheel sensor differs from the signal sent at the previous time by more than the specified value.

PROBABLE CAUSES



DIAGNOSIS

STEP 1. M.U.T.-III CAN bus diagnostics


caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
(1)Connect M.U.T.-III to the 16-pin diagnosis connector.
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the check result normal?

Go to Step 2.

Repair the CAN bus line (Refer to GROUP 54C, CAN bus line Diagnostic flow ). Then go to Step 4.

STEP 2. M.U.T.-III diagnosis code


Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Check if the diagnosis code is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is code No.U1204 set?

Replace the steering wheel sensor. Then go to Step 3.

It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction .

STEP 3. M.U.T.-III diagnosis code


Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Check if the diagnosis code is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is code No.U1204 set?

Replace the hydraulic unit (integrated with ASTC-ECU.) Then go to Step 4.

It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction .

STEP 4. Check whether the diagnosis code is reset.


Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Check if the diagnosis code is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is code No.U1204 set?

Go to Step 1.

The procedure is complete.