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.
DIAGNOSIS FUNCTION
WCM checks if the data from the engine-ECU is received via the CAN bus line. When WCM
cannot receive the engine ECU data, it sets the diagnosis code No. B1731.
JUDGEMENT CRITERIA
WCM determines that the abnormality is present, if it cannot receive the data [ETACS-ECU
is sending the engine data to WCM via the CAN bus line] from the engine ECU via the
CAN bus line when the ignition switch is turned ON.
PROBABLE CAUSES
Malfunction of CAN bus line
Damaged wiring harness and connectors
Engine-ECU malfunction
Malfunction of WCM
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. 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 WCM and register the ID codes (Refer to ).
Register the ID codes and go to Step 3.
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 the engine ECU and register the chassis number and key codes [Refer
to GROUP 00 - How to Perform Chassis Number (Chassis No.) Writing ].
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting 
).
On completion, go to Step 2.