When diagnosis
code No. B1A28 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 sets diagnosis code No. B1A28 when the WCM’s key certification result and
the engine-ECU’s starting condition do not match.
JUDGEMENT CRITERIA
WCM determines that the abnormality is present, if the key certification result and the
engine-ECU’s starting condition do not match after the engine start permission communication
is completed.
PROBABLE CAUSES
Malfunction of CAN bus line
Malfunction of WCM
Engine-ECU malfunction
Chassis number registered in engine-ECU unmatched
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 ).
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 <2000> or GROUP
13C - Troubleshooting <3000> or
GROUP 13D - Troubleshooting <2400> or
GROUP 13E - Troubleshooting <2200>).
Go to Step 3.
STEP 3. Diagnosis code check
Q.
Other than code No. B1A28, is diagnosis code No. B1761 or B2206 set?
Perform troubleshooting for each diagnosis code. Refer to <B1761>, <B2206>.
Go to Step 4.
STEP 4. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set.
(1)Turn the ignition switch from the LOCK (OFF) position to the ON position.
(2)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 5.
The diagnosis is complete.
STEP 5. Check whether the diagnosis code is reset.
Recheck if the diagnosis code is set.
(1)Turn the ignition switch from the LOCK (OFF) position to the ON position.
(2)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 
).