DTC B1731: Engine control module communication timeout: Diagnosis

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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.
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.
Fig 1: Connecting Scan Tool MB991958 To Data Link Connector
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

Q: Is the CAN bus line found to be normal?
1. YES: Go to Step 2.
2. NO: Repair the CAN bus line. (Refer to DIAGNOSIS ).
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?
1. YES: Troubleshoot the MFI system (Refer to DIAGNOSTIC TROUBLE CODE TABLE (2. 0L Engine Non-turbo), DIAGNOSTIC TROUBLE CODE TABLE (2. 0L Engine Turbo) or DIAGNOSTIC TROUBLE CODE TABLE (2. 4L Engine)).
2. 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?
1. YES: Go to Step 5.
2. 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?
1. YES: Replace WCM and register the ID codes (Refer to ID CODES REGISTRATION PROCEDURE ). After registering the ID codes, go to Step 6.
2. NO: The trouble can be an intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
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?
1. YES: Replace the engine control module and record the VIN (Refer to HOW TO PERFORM VEHICLE IDENTIFICATION NUMBER (VIN) WRITING ). Then go to Step 6.
2. 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?
1. YES: Replace the ETACS-ECU.
2. NO: The procedure is complete.