If diagnosis code U1102 is set in the A/T-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
Current trouble
Connector(s) or wiring harness in the CAN bus lines between the ASTC-ECU and the
A/T-ECU, the power supply system to the ASTC-ECU, the ASTC-ECU itself, or the A/T-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 ASTC-ECU and the A/T-ECU, and the power supply system to the ASTC-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 -
How to Cope with Intermittent Malfunctions ).
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, Explanation about the M.U.T.-III CAN Bus Diagnostics ).
PROBABLE CAUSES
Damaged wiring harness or connector
Malfunction of the ASTC-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 busline diagnosis.
Q.
Is the check result normal?
Go to Step 2.
Repair the CAN busline (Refer to GROUP54C, Diagnosis -
Can Bus Diagnostic
Chart ), and then go to Step 4.
STEP 2. M.U.T.-III other system diagnosis codes
Check whether the ASTC system diagnosis codes are set or not.
Q.
Is the diagnosis code output?
YES : Diagnose the ASTC system (Refer to GROUP 35C, Troubleshooting ).
Go to Step 3.
STEP 3. M.U.T.-III diagnosis code
Reconfirm whether the diagnosis codes are output from A/T-ECU.
(1)Erase the diagnosis code.
(2)Turn the ignition switch to ON position.
(3)Check if the diagnosis code is set.
Q.
Is the diagnosis code output?
Go to Step 4.
Intermittent malfunction in CAN busline between ASTC-ECU and A/T-ECU (Refer to
GROUP 00 -
How to Use Troubleshooting/Inspection Service Points -
How to Cope
with Intermittent Malfunction ).
STEP 4. Replace the ASTC-ECU
After replacing the ASTC-ECU, re-check the A/T diagnosis code output.
).
