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


caution
  • If diagnosis code No.U1101 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.

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set if ASTC-ECU cannot receive the signal sent from the A/T-ECU for a certain period.

PROBABLE CAUSES

  • Damaged harness or connector.
  • Malfunction of the A/T-ECU.
  • Malfunction of the ASTC-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 line (Refer to GROUP 54C - CAN Bus Diagnostics Table ). Then go to Step 5.

STEP 2. M.U.T.-III other diagnosis code
Check whether the diagnosis code No. U1101 is set by another ECU.

Q. Is the diagnosis code set?
Replace the A/T-ECU (Refer to GROUP 23A - A/T-ECU ) Then go to Step 5.
Go to Step 3.

STEP 3. M.U.T.-III other diagnosis code
Check whether the diagnosis code is set by A/T-ECU.

Q. Is any diagnosis code set?
Perform troubleshooting for A/T-ECU (Refer to GROUP 23A - Troubleshooting ). Then go to Step 5.
Go to Step 4.

STEP 4. M.U.T.-III diagnosis code
(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.U1101 set?
Replace the hydraulic unit (integrated with ASTC-ECU) (Refer to ). Then go to Step 5.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

STEP 5. Check whether the diagnosis code is reset.
(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.U1101 set?
Go to Step 1.
The procedure is complete.