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DTC B1731 ENG ECU authentification timeout
 
 
caution
  • When DTC 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
If the necessary data cannot be received from ECM via CAN bus line during the engine starting certification with ECM, KOS&OSS-ECU determines that a problem has occurred, and sets DTC B1731. At the same time, KOS&OSS-ECU displays the immobilizer certification system inspection warning to the combination meter.
 
 
JUDGMENT CRITERIA
Check Conditions
  • At engine starting certification
Judgment Criterion
  • At the engine starting certification with ECM, necessary data cannot be received from ECM via CAN bus line.
 
 
PROBABLE CAUSES
  • Malfunction of the CAN bus line
  • Malfunction of ECM
  • Malfunction of KOS&OSS-ECU
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), diagnose the CAN bus line
Use the scan tool (M.U.T.-IIISE) to diagnose the CAN bus lines.
Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C - Diagnosis ).
 
STEP 2. Using scan tool (M.U.T.-IIISE), check the other system DTC.
(1) Check that the vehicle power can be turned ON and engine is started.
(2) Check the DTC of ECM.
Is the DTC set?
Troubleshoot the ECM (Refer to GROUP 13A - Diagnosis ). Then go to Step 3.
Go to Step 3.
 
STEP 3. Check whether the DTC is set again.
(1) Operate the engine switch several times within five seconds without depressing the brake pedal to turn ON and OFF the power supply mode.
(2) Check again if the DTC is set in the KOS&OSS-ECU.
Is the DTC set?
Replace the KOS&OSS-ECU and register the ID codes (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 DTC is set again.
Check again if the DTC is set in the KOS&OSS-ECU.
Is the DTC set?
Replace the ECM (Refer to GROUP 13A - ECM ).
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).