When the Check Engine light turns on there will be at least one diagnostic fault code stored in the Engine Computer. Many auto parts stores will read them for you for free. That's the place to start. Those codes will lead you to the circuit or system with the problem, not necessarily the defective part.
Based on the multiple symptoms, you might suspect the generator. GM has a real lot of trouble with them. They often develop excessive voltage spikes that interfere with sensor signals for the many various computers. As a test, you can unplug it then see if the engine runs better. If it does, have the generator checked. It is real common to go through four to six of them in the life of the truck. What many professionals are finding out is to reduce the repeat failures, you should replace the battery at the same time. It will still work fine in older cars from before 1987 but as they age they lose their ability to dampen those voltage spikes.
caradiodoc
Feb 8, 2011 at 12:44 AM
