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There are 3 possible causes for the symptoms you describe:
(1) There may be a loose or damaged electrical plug at the back of the instrument panel, causing loss of serial data input to the instrument cluster.
(2) There may be an internal instrument cluster fault in the cluster itself; it is serviced as an assembly. If a cluster is determined to be the problem, it must be sent in to a GM service center for repair and programming.
(3) The vehicle may be experiencing a fault related to the serial data communications network. The instrument panel receives data from various modules in the other parts of the vehicle; if data communication is lost with the data bus then the instrument cluster may turn on all warning lights at once and otherwise perform erratically.
Accurate diagnosis of the failure will require use of a Vetronix tech-2 scan tool to monitor vehicle data bus communications in order to isolate the problem down to an internal IPC fault, a communication fault due to some other component on the data bus bringing the bus down, or an electrical connection. There really is very little you can do to accurately diagnose this particular type of problem without the factory scan equipment. Therefore, i would suggest taking it in to the GM dealer for diagnosis. If the IPC is found to be at fault, you will need to send it in for repair through the GM dealer anyway, so having it diagnosed there would save time.
I hope this is helpful to you; if so, an accept would be most appreciated! Thanks!
No, I'm afraid there is no magical shortcut to locating the source of the electrical problems you are having. i did spend about 20 minutes going through repair databases and TSB lists researching your problem; there ARE no pattern failures on record causing the symptoms you describe.
Unfortunately, sometimes you either have to pay a trained professional to fix some of the more complicated problems such as you are experiencing, or invest the time to learn how the system works and purchase the expensive diagnostic equipment required to be able to troubleshoot it yourself. The electrical system on your particular vehicle is extremely complex, and involves many microprocessors communicating over a computer network. Diagnosing and repairing it is not as easy as "tightening a loose ground wire", although 20 years ago things were much simpler and often you could narrow down the cause to something so obvious.
The answer I provided you is accurate, and is not copied and pasted from a book somewhere. I have 26 years of electronic diagnostic experience on this type of problem, do thsi for a living, and am highly paid to diagnose such failures in person. For the $20 you offered for help, I provided you a very accurate professional opinion as to the possible causes of your problem, and told you what is needed to locate and correct it as cheaply and quickly as possible. If you are not experienced in electronic diagnosis and repairs, and do not have the necessary scan equipment to communicate with the computer network in the vehicle to get the information required to locate the source of the problem, there is no possible way someone can walk you through diagnosis of a problem of this type. I thought I was doing you a good service by explaining the possible causes, what is required to isolate the problem, and saving you a LOT of time and probably a lot of wasted money by taking the car to a shop without the necessary equipment and paying them $75 or so an hour to discover they couldn't fix it either. SOme types of problems can be fixed in the backyard with little in the way of tools or experience; some types of problems require a certain level of training and experience and some tools and equipment, and then there are some problems (such as what you are experiencing) that require a high level of training and some very expensive tools to be able to fix quickly and accurately. I'm sorry if that is not what you wanted to hear, but that is the reality.
And, incidentally, the reference materials we use to provide you with the answer you requested cost far more than $20; in our shop we spend in teh vicinity of $10,000+ a year for software and information service subscriptions;and many expensive hours in factory level training to gain the knowledge to be able to help you (as do all modern repair facilities. ) You will not find ANY of the information I provided to you in a $20 book.