Have you had all the moduels check for code's ? Not autozone or anywhere else like that . Need professional type . Could have a GMLAN serial data network problem . All the control modules on the vehicle , PCM/ECM , BCM , instrument cluster , radio , air bag's , ABS , electric power steering etc... all share information on the data network . GMLAN is GM'S version of C.A.N. - controller area network .
How to Diagnose Controller Area Network CAN Checking for communication problem codes is the first thing to do with problems like you are having . Have you taken it to a Chevy dealer ? This does sound like a data network problem .
The communication among control modules is performed through the GMLAN high speed serial data circuit and the GMLAN low speed serial data circuit. The modules that need real time communication are attached to the high speed GMLAN network. The body control module (BCM) is the gateway between the networks. The purpose of the gateway is to translate serial data messages between the GMLAN high speed buss and the GMLAN low speed buss. The gateway will interact with each network according to that network's transmission protocol. Refer to Body Control System Description and Operation for more information about the gateway.
The powertrain control module (PCM) on this vehicle, uses a class 2 serial data buss. The class 2 buss is only used for diagnostics and the service programming system (SPS). During normal vehicle operations, there is no communications over the class 2 serial data buss. Normal vehicle operational messaging for the PCM is sent over the PCMs GMLAN high speed serial data buss.
Could be a simple fix , i see them all the time . Lose ground wire for one of the modules . That includes the instrument cluster , it also has a microprocessor inside an can set DTC'S -diagnostic trouble codes . Finding a U code in one of the modules would shorten diagnostic time .
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