When the diagnosis
code No. B1731 is set, be sure to diagnose the CAN bus line.
When replacing the ECU, always check that the communication circuit is normal.
DIAGNOSTIC FUNCTION
KOS-ECU checks that the engine-ECU data has been received via the CAN bus lines, and if
not, sets the diagnosis code No. B1731.
JUDGEMENT CRITERIA
If no data [ETACS transmits engine random number data to KOS-ECU via the CAN
bus lines] is received from the engine ECU via the CAN bus lines when the ignition
switch is turned to ON position, it is judged as abnormal.
PROBABLE CAUSES
Malfunction of CAN bus line
Malfunction of KOS-ECU
Malfunction of engine-ECU
Damaged wiring harness and connectors
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 - Troubleshooting ).
On completion, go to Step 2.
STEP 2. M.U.T.-III other system diagnosis code
Check whether an engine-related diagnosis code is set.
Q.
Is the diagnosis code set?
Perform troubleshooting for the engine (Refer to GROUP 13A - Troubleshooting ).
Go to Step 3.
STEP 3. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.
(3)Check if the diagnosis code is set.
Q.
Is the diagnosis code set?
Replace KOS-ECU and register the ID codes (Refer to ).
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting 
).
On completion, go to Step 2.