Wireless Control Module (WCM)
DTC B1731: Engine control module communication timeout
CAUTION:
- When the 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 the 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 ETACS-ECU
- Damaged wiring harness and connectors
- 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 (Vehicles with CAN communication system)
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 line. CAN Bus Diagnostics Chart).
STEP 2. Using scan tool MB991958, read the 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 Multiport Fuel Injection (MFI) [2.0L Engine Non-turbo], Diagnostic trouble code chart Multiport Fuel Injection (MFI) [2.0L Engine Turbo] or Diagnostic trouble code chart Multiport Fuel Injection (MFI) [2.4L Engine].
NO Go to Step 3.
STEP 3. Using scan tool MB991958, read the other system diagnostic trouble code.
Check if DTC U0100 is set to ETACS-ECU.
Q. Is the DTC set?
YES Go to Step 5.
NO Go to Step 4.
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 WCM and register the ID codes (Refer to ID registration procedure manual
- ID codes registration judgement table). After registering the ID codes, go to Step 6.
NO The trouble can be an intermittent malfunction How to Cope With Intermittent Malfunctions).
STEP 5. 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 How to Perform Vehicle Identification Number (VIN) Writing).
Then go to Step 6.
NO The procedure is complete.
STEP 6. 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 ETACS-ECU.
NO The procedure is complete.