Code No. B1731: Communication Error with the Engine-ECU

caution

If diagnosis code No.B1731 is set in the immobilizer-ECU, diagnose the CAN bus lines.

caution

Whenever the ECU is replaced, ensure that the input and output signal circuits are normal.

TROUBLE JUDGMENT

If the immobilizer-ECU cannot receive any signals from the engine-ECU, diagnosis code B1731 will be set.

COMMENT ON TROUBLE SYMPTOM

Connector(s) or wiring harness in the CAN bus lines between the immobilizer-ECU and the engine-ECU, the power supply system to the engine-ECU, the engine-ECU itself, or the immobilizer-ECU itself may be defective.

PROBABLE CAUSES

Malfunction of engine-ECU
Malfunction of immobilizer-ECU
Damaged harness wires and connectors

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 54D - Troubleshooting

). Repair the CAN bus line and go to Step 2.

STEP 2. Check whether the diagnosis code is reset.

Check again if the diagnosis code is set.

(1)Erase the diagnosis code.

(2)Turn the ignition switch to the "LOCK" (OFF) position once, and then turn it to the "ON" position again.

(3)Check that diagnosis code No.B1731 is not set as a current trouble.

Q. Is diagnosis code No.B1731 set?

Replace the immobilizer-ECU and register the ID codes (Refer to

). After registering the ID codes, go to Step 3.

The diagnosis is complete. If another diagnosis code is set, refer to Diagnosis Code Chart

STEP 3. Check whether the diagnosis code is reset.

Recheck if the diagnosis code is set.

(1)Erase the diagnosis code.

(2)Turn the ignition switch to the "LOCK" (OFF) position once, and then turn it to the "ON" position again.

(3)Check that diagnosis code No.B1731 is not set as a current trouble.

Q. Is diagnosis code No.B1731 set?

Replace the engine-ECU and resister the ID code (Refer to

The diagnosis is complete. If another diagnosis code is set, refer to Diagnosis Code Chart