GMC Troubleshooting Questions? Ask a Mechanic for Answers
Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.Any time you have a mode door concern and or temp control issue the system should set and store a fault code and or codes, in order to determine what is failing you are going to need to start first with scanning the system to see what the fault code and or codes are that should be setting. If you can get this done and post back with the results I will try and help you determine the cause.