B1731

DTC B1731: Immobilizer Communication Failure

DTC SET CONDITION
If the ETACS-ECU cannot receive the signal from the ECM or PCM , DTC B1731 will be set.

TECHNICAL DESCRIPTION (COMMENT)
If a data error is detected in the ECM or the PCM , diagnosis code No. B1731 will be set.

TROUBLESHOOTING HINTS
- Damaged wiring harness or connector.
- Malfunction of the ECM or the PCM
- 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.

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).

1. 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 (Refer to Information Bus - Precautions on how to repair the Can Bus lines.

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 or the PCM , and then record the VIN. 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. Retest the system.

NO: The procedure is complete.