Code No. B1731
ENG ECU authentification timeout
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- When 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.
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DIAGNOSTIC FUNCTION
If the necessary data cannot be received from engine-ECU via CAN bus line during the engine starting
certification with engine-ECU, KOS&OSS-ECU determines that a problem has occurred,
and sets diagnosis code No.B1731. At the same time, KOS&OSS-ECU displays the immobilizer certification
system inspection warning to the combination meter.
JUDGEMENT CRITERIA
Check Conditions
- At engine starting certification
Judgement Criterion
- At the engine starting certification with engine-ECU, necessary data cannot be received
from engine-ECU via CAN bus line.
PROBABLE CAUSES
- Malfunction of the CAN bus line
- Malfunction of engine-ECU
- Malfunction of KOS&OSS-ECU
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnostics
Use the 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
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(1)Check that the vehicle power can be turned "ON" and engine is started.
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(2)Check the diagnosis code of engine-ECU.
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Q.
Is the diagnosis code set?
Troubleshoot the engine-ECU (Refer to GROUP 13A - Troubleshooting ). Then
go to Step 3.
Go to Step 3.
STEP 3. Check whether the diagnosis code is set again.
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(1)Turn the engine switch "OFF" and "ON" several times without depressing the brake
pedal (Perform quickly within approximately five seconds).
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(2)Check again if the diagnosis code is set in the KOS&OSS-ECU.
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Q.
Is the diagnosis code set?
Replace the KOS&OSS-ECU and register the chassis number (Refer to ).
Then go to Step 4.
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection
Service Points - How to Cope with Intermittent Malfunction ).
STEP 4. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set in the KOS&OSS-ECU.
Q.
Is the diagnosis code set?
Replace the engine-ECU.
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection
Service Points - How to Cope with Intermittent Malfunction ).