Code No.B1731 ENG ECU authentication timeout
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- When diagnosis code No. B1731 is stored, be sure to diagnose the CAN bus line.
- When replacing the ECU, always check that the communication circuit is normal.
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DIAGNOSIS FUNCTION
ETACS-ECU checks if the data from the engine-ECU is received via the CAN bus line. When ETACS-ECU cannot receive the engine-ECU data, it stores diagnosis code No. B1731.
JUDGEMENT CRITERIA
ETACS-ECU determines that the abnormality is present, if it cannot receive the data 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
- Malfunction of Engine-ECU
- Malfunction of ETACS-ECU
DIAGNOSIS PROCEDURE
STEP 1. Check whether the diagnosis code is stored again.
Recheck if the diagnosis code is stored in the ETACS-ECU.
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(1)Erase the diagnosis code.
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(2)Remove the ignition key from key cylinder and insert it again then turn the ignition switch from the Lock (OFF) position to the ON position.
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(3)On completion, check that the diagnosis code is not stored again.
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Q.
Is the diagnosis code stored?
Go to Step 2.
There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction 
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STEP 2. 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 3.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ). On completion, go to Step 3.
STEP 3. M.U.T.-III other system diagnosis code
Check whether an engine-related diagnosis code is stored.
Q.
Is the diagnosis code stored?
Perform troubleshooting for the engine (Refer to GROUP 13A - Diagnosis Code Chart <2000, 2400>, GROUP 13B -Troubleshooting <3000>).
Go to Step 4.
STEP 4. M.U.T.-III other system diagnosis code
Check if diagnosis code No.U0100 is stored in ETACS-ECU.
Q.
Is the diagnosis code stored?
Go to Step 6.
Go to Step 5.
STEP 5. Check whether the diagnosis code is stored again.
Recheck if the diagnosis code is stored in the ETACS-ECU.
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(1)Remove the ignition key from key cylinder and insert it again then turn the ignition switch from the Lock (OFF) position to the ON position.
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(2)Check if the diagnosis code is stored.
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Q.
Is the diagnosis code stored?
Replace ETACS-ECU (Refer to ) and register the ID codes (Refer to ).
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
STEP 6. Check whether the diagnosis code is stored again.
Recheck if the diagnosis code is stored in the ETACS-ECU.
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(1)Remove the ignition key from key cylinder and insert it again then turn the ignition switch from the Lock (OFF) position to the ON position.
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(2)Check if the diagnosis code is stored.
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Q.
Is the diagnosis code stored?
Replace the engine-ECU and register the chassis number and key codes [Refer to GROUP 00 - How to Perform Chassis Number (Chassis No.) Writing ].
The diagnosis is complete.