Code No. U0101: Transmission CAN timeout <A/T>

caution

If diagnosis code U0101 is set in the transfer-ECU, always diagnose the CAN main bus line.
Whenever the ECU is replaced, ensure that the communication circuit is normal.

DIAGNOSIS CODE SET CONDITIONS

Current trouble

Connector(s) or wiring harness in the CAN bus line between the A/T-ECU and the transfer-ECU, the power supply system to the A/T-ECU, the A/T-ECU itself, or the transfer-ECU may be defective.

Past trouble

Carry out diagnosis with particular emphasis on connector(s) or wiring harness in the CAN bus lines between the A/T-ECU and the transfer-ECU, and the power supply system to the A/T-ECU. For diagnosis procedures, refer to "How to cope with past trouble" (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points

note

For a past trouble, you may not find it by the M.U.T.-III CAN bus diagnostics even if there is any failure in CAN bus lines. In this case, refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points

. and check the CAN bus lines. You can narrow down the possible cause of the trouble by referring to the diagnosis code, which is set regarding the CAN communication-linked ECUs (Refer to GROUP 54C - CAN Bus Line Diagnostic Flow

PROBABLE CAUSES

Damaged wiring harness or connector
Malfunction of the transfer-ECU
Malfunction of the A/T-ECU

DIAGNOSIS PROCEDURE

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

Using M.U.T.-III, perform CAN bus line diagnosis.

Q. Is the check result normal?

	Go to Step 2.

	Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ). and then go to Step 6.

STEP 2. M.U.T.-III other system diagnosis codes

Check whether the A/T-ECU set a diagnosis code.

Q. Is the diagnosis code set?

	YES : Diagnose the automatic transmission (Refer to GROUP 23A - Troubleshooting - Diagnosis Code Chart ).

	Go to Step 3.

STEP 3. Check the M.U.T.-III Diagnosis code for other systems

Is diagnosis code No. U0101 set in the other ECU, which communicates with the A/T-ECU via CAN?

Q. Is the diagnosis code set?

	Go to Step 4.

	Go to Step 5.

STEP 4. Check whether the diagnosis code is set again.

Check again if the diagnosis code is set in the transfer-ECU.

(1)Erase the diagnosis code.

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

(3)On completion, check whether the diagnosis code is set again.

Q. Is the diagnosis code set?

	Replace the A/T-ECU (Refer to GROUP 23A - A/T-ECU ). After replacing the ECU, carry out the CAN bus diagnostics. Then go to Step 6.

	A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the engine-ECU and the transfer-ECU (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 5. Check whether the diagnosis code is set again.

Check again if the diagnosis code is set in the transfer-ECU.

(1)Erase the diagnosis code.

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

(3)On completion, check that the diagnosis code is not set again.

Q. Is the diagnosis code set?

	Replace the transfer-ECU (Refer to ). After replacing the ECU, carry out the CAN bus diagnostics. Then go to Step 6.

	A poor connection, open circuit or other intermittent malfunction is present in the CAN bus lines between the engine-ECU and the transfer-ECU (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 6. Check whether the diagnosis code is set again.

Recheck if the diagnosis code is set in the transfer-ECU.

(1)Erase the diagnosis code.

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

(3)On completion, check that the diagnosis code is set again.

Q. Is the diagnosis code set?

	Return to Step 1.

	The procedure is complete.