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.
note
Diagnosis code No.B1731 is always set along with MPI system diagnosis code No.U1117.
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 54C -
Troubleshooting ). Repair
the CAN bus line and go to Step 3.
STEP 2. Check whether the diagnosis code is reset.
Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "LOCK" (OFF) position once, and then turn it to
the ON position again.
(2)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)Turn the ignition switch to the "LOCK" (OFF) position once, and then turn it to
the ON position again.
(2)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 .