Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
When it goes into limp mode, do you know which trouble codes are setting?
Do you know which they were specifically? They could be circuit malfunction codes, position codes, correlation codes, etc. It sounds like you have replaced just about everything in an attempt to fix it, if I have the specific codes I might be able to help you pinpoint it rather than just throw parts at it.
Ok. When you turn the key to the run position can you hear the fuel pump buzz for a few seconds? It should make an audible buzzing sound for about 3 seconds each time the key is turned to run.
Are you getting power to the fuel pump relay?
The PCM B fuse powers the relay, check to make sure you are getting 12 volts to the PCM B fuse.
Next, check side of the fuel pump relay for a picture that looks like a map. It should like like this picture.
It will have the pins labeled and the pins that correspond to the parts I circled in red should have power. The one on the right, that leads to the PCM B fuse will have power all the time. The one on the left will have power with the key in run (but only for 3 seconds after the key is turned).
So pin 30 should have 12 volts constant, pin 86 should have 12 volts when key in run for 3 seconds. Pin 85 will be ground, and pin 87 should feed the fuel pump. So if you unplug the relay and put a jumper wire (or paperclip) across pin 30 to 87 it should make the fuel pump run- this would test whether the fuel pump is working. It will pump for as long as you have the jumper in since this would be bypassing the relay circuit and feed voltage right to the pump- assuming you have 12 volts on pin 30 like you should.
I'm leaving the shop for the day, I'll check back in this evening to see if you need additional info.
Weird. Do you have 12 volts on any of the pins?
Also, 86 might have ground and 85 voltage with key in the run- my diagram doesn't label the pin numbers and I can't remember off memory.
If you jumped 87 to 30 and the fuse blew that means the gray wire from the relay to the fuel pump is shorted to ground somewhere or the fuel pump is defective.
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Does the engine crank but not start or does it not crank at all?
If you spray starting fluid or fuel in the intake duct will it start for a few seconds?
If it does then you may not be getting injector pulse which is usually triggered by the crank position sensor. If you have a scan tool you can use it to look for an RPM signal while cranking, if you don't have an RPM signal when cranking then the crank position sensor is dead.