Wireless Control Module (WCM)

DTC B1731: Engine control module communication timeout

CAUTION:
- When DTC B1731 is set, be sure to diagnose the CAN bus line.
- When replacing the ECU, always check that the communication circuit is normal.

DTC SET CONDITION
WCM checks that the engine control module data has been received via the CAN bus lines, and if not, sets DTC No. B1731.

TECHNICAL DESCRIPTION (COMMENT)
If no data [ETACS transmits engine random number data to WCM via the CAN bus lines] is received from the engine control module via the CAN bus lines when the ignition switch is turned to ON position, it is judged as abnormal.

TROUBLESHOOTING HINTS
- Malfunction of CAN bus line
- Malfunction of WCM
- Malfunction of engine control module

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (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 line (Refer to Controller Area Network, Diagnosis).

STEP 2. Using scan tool MB991958, check for engine control module diagnostic trouble code.

Check again if the DTC is set to the engine control module.

Q: Is the DTC set?

YES: Troubleshoot the MFI system (Refer to MFI, Diagnostic trouble code chart).

NO: Go to Step 3.

STEP 3. Recheck for diagnostic trouble code.

Check again if the DTC is set to the WCM.
1. Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
2. Check if DTC is set.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES: Replace WCM and register the ID codes (Refer to ID Codes Registration Judgment Table). After registering the ID codes, go to Step 4.

NO: The trouble can be an intermittent malfunction (Refer to General (Body and Chassis) - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction).

STEP 4. Recheck for diagnostic trouble code.

Check again if the DTC is set to the WCM.

1. Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
2. Check if DTC is set.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES: Replace the engine control module and record the VIN (Refer to General (Body and Chassis - How To Perform Vehicle Identification Number (VIN) Writing).

NO: The procedure is complete.