Code No. U1101: A/T-ECU timeout error

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 (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
If diagnosis code U1101 is set in ASTC-ECU, always diagnose the CAN bus line. If there is any fault in the CAN bus lines, an incorrect diagnosis code may be set. In this case, the set diagnosis code is not highly reliable.
Whenever ECU is replaced, ensure that the CAN bus lines are normal.
When the hydraulic unit (integrated with ASTC-ECU) is replaced, always carry out the calibration of the steering wheel sensor and the G and yaw rate sensor (Refer to ).

OPERATION

The ASTC-ECU communicates with the A/T-ECU via the CAN bus lines.

DIAGNOSIS CODE SET CONDITIONS

The ASTC-ECU receives the A/T control-related signals from the A/T-ECU via the CAN bus lines. When these signals cannot be received, the ECU sets this diagnosis code.

PROBABLE CAUSES

Malfunction of ETACS-ECU
The ASTC-ECU, which was used on another vehicle, is installed on this vehicle.
The ETACS-ECU, which was used on another vehicle, is installed on this vehicle
The CAN bus line is defective
Malfunction of the A/T-ECU
Malfunction of the hydraulic unit assembly (integrated with ASTC-ECU)

DIAGNOSIS PROCEDURE

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

Use the M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?

	Go to Step 3.

	Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ). On completion, go to Step 2.

STEP 2. Diagnosis code recheck after resetting CAN bus lines

Q. Is diagnosis code No. U1101 set?

	Go to Step 3.

	This diagnosis is complete.

STEP 3. Check for diagnosis codes of other systems.

Check if the diagnosis code is set in the A/T-ECU (Refer to GROUP 23A - Diagnosis Code Chart

Q. Is the diagnosis code set?

	Follow the relevant diagnosis code procedure (Refer to GROUP 23A - Diagnosis Code Chart ). Then go to Step 5.

	Go to Step 4.

STEP 4. Check for diagnosis codes of other systems.

Check whether an transmission "time-out" related diagnosis code is set in other ECUs.

Q. Is the diagnosis code set?

	Replace the A/T-ECU (Refer to GROUP 23A - A/T-ECU ). Then go to Step 8.

	Go to Step 5.

STEP 5. ETACS-ECU coding data check

Use M.U.T.-III, check if any abnormality is present to the coding data which are stored in the ETACS-ECU.

Q. Is the check result normal?

	Go to Step 6.

	Replace the ETACS-ECU (Refer to GROUP 54A - ETACS-ECU ). Then go to Step 8.

STEP 6. Check part number of ASTC-ECU

Check the part number of ASTC-ECU.

Q. Is the check result normal?

	Go to Step 7.

	Replace the hydraulic unit assembly (integrated with ASTC-ECU) (Refer to ). Then go to Step 8.

STEP 7. Check whether the diagnosis code is set again.

Check again if the diagnosis code is set.

(1)Turn the ignition switch to the "LOCK" (OFF) position.

(2)Turn the ignition switch to the "ON" position.

(3)Erase the diagnosis code.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

(5)Turn the ignition switch to the "ON" position.

(6)Check if the diagnosis code is set.

Q. Is diagnosis code No. U1101 set?

	Replace the hydraulic unit assembly (integrated with ASTC-ECU) (Refer to ). Then go to Step 8.

	The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

STEP 8. Check whether the diagnosis code is set again.

Check again if the diagnosis code is set.

(1)Turn the ignition switch to the "LOCK" (OFF) position.

(2)Turn the ignition switch to the "ON" position.

(3)Erase the diagnosis code.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

(5)Turn the ignition switch to the "ON" position.

(6)Check if the diagnosis code is set.

Q. Is diagnosis code No. U1101 set?

	Return to Step 1.

	The procedure is complete.