B1731

DTC B1731: Immobilizer Communication Failure

CAUTION:
Whenever the engine is started by using the remote control engine starter (available as a dealer optional equipment), DTC B1731 will be set.This DTC B1731 will be erased from current trouble list when the engine is started by a registered ignition key in the usual way, and then will be stored as a historic trouble.Therefore, on vehicles with remote control engine starter, DTC B1731 does not indicate a malfunction if it is stored as a historic trouble. If so, no action is needed.

DTC SET CONDITION

If the ETACS-ECU cannot receive the signal from the ECM [M/T] or PCM [A/T], DTC B1731 will be set.

TECHNICAL DESCRIPTION (COMMENT)

If a data error is detected in the ECM [M/T] or the PCM [A/T], diagnosis code No. B1731 will be set.

TROUBLESHOOTING HINTS

- Damaged wiring harness or connector.
- Malfunction of the ECM[ M/T] or the PCM[ A/T]
- Malfunction of the ETACS-ECU.

DIAGNOSIS

Required Special Tools:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.





(1)
CAUTION:
To prevent damage to scan tool (MB991958), always turn the ignition switch to the "LOCK"
(OFF) position before connecting or disconnecting scan tool (MB991958).

Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the CAN bus line found to be normal?

YES Go to Step 2.

NO Repair the CAN bus lines Precautions on How to Repair the CAN Bus Line(s)).

STEP 2. Recheck for diagnostic trouble code.

Recheck if the diagnostic trouble code is set.





(1)Turn the ignition switch to "ON" position.
(2)Erase the diagnostic trouble code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to "ON" position.
(5)Check if the diagnostic trouble code is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the diagnostic code set?

YES Replace the ECM [M/T] or the PCM [A/T], and then record the VIN (Refer to Encrypted Code Registration Criteria Table). Then go to Step 3.

NO The procedure is complete.

STEP 3. Recheck for diagnostic trouble code.

Recheck if the diagnostic trouble code is set.





(1)Turn the ignition switch to "ON" position.
(2)Erase the diagnostic trouble code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to "ON" position.
(5)Check if the diagnostic trouble code is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the diagnostic code set?

YES Replace the ETACS-ECU, and then record the VIN. Then, register the encrypted code again (Refer to Encrypted Code Registration Criteria Table). Retest the system.

NO The procedure is complete.