Code No. B1731 ENG ECU authentification timeout <Vehicles with M/T or 4D5>

caution

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.

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

(1)Check that the vehicle power can be turned ON and engine is started.

(2)Check the diagnosis code of engine-ECU.

Q. Is the diagnosis code set?

Troubleshoot the engine-ECU (Refer to GROUP 13B - Troubleshooting <6B3>, GROUP 13C - Troubleshooting <4N1> or GROUP 13E - Troubleshooting

<4D5>). Then go to Step 3.

Go to Step 3.

STEP 3. Check whether the diagnosis code is set again.

(1)Operate the engine switch several times within five seconds without depressing the brake pedal <A/T> or the clutch pedal <M/T> to turn on and off the power supply mode.

(2)Check again if the diagnosis code is set in the KOS&OSS-ECU.

Q. Is the diagnosis code set?

Replace the KOS&OSS-ECU and register the chassis number. 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 (Refer to GROUP 13B - Engine-ECU <6B3>, GROUP 13C - Engine-ECU <4N1> or GROUP 13E - Engine-ECU

<4D5>).

Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).