For a complete wiring diagram Refer to Section 8WWhen Monitored:Continuously while the system is active.Set Condition:An invalid message has been received over the bus from the Front Control Module (FCM).Possible CausesINTERMITTENT DTCCAN BUS OPEN OR SHORTED CONDITIONFRONT CONTROL MODULE (FCM)ENGINE CONTROL MODULE (ECM)Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)1. ACTIVE DTCDiagnose all CAN B and C communication DTCs before continuing.Ignition on, engine not running.With a scan tool, view DTCs.Is the status Active for this DTC?YesGo To 2 NoRefer to the INTERMITTENT CONDITION Diagnostic Procedure.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)2. COMMUNICATION DTCS PRESENT IN THE TOTALLY INTEGRATED POWER MODULE (TIPM)With a scan tool check for DTCs in the TIPM.Are there any CAN bus DTCs active in the TIPM at this time?YesRefer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - DIAGNOSIS AND TESTING for additional vehicle communication diagnostic procedures.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoReplace and program the Engine Control Module (ECM) in accordance with the Service Information.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)