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Mike S.
Mike S., ASE Certified Technician
Category: GMC
Satisfied Customers: 7230
Experience:  GMC N.A.I.S.E. Certified Auto-Mechanic
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I have a 2002 GMC 3/4 ton HD. The problem is sometimes it

Customer Question

I have a 2002 GMC 3/4 ton HD. The problem is sometimes it doesn't start. I get in and turn the key. Nothing, I have battery power, but it doesn't make contact. It's like it's in drive. Please help!
JA: Is the car in "Park" or "Neutral?" Do you know if your car has a "wheel lock" feature?
Customer: It is in park. I move the lever down to L4 and back up to park, turning the key each time i come to a differant station. Sometimes this works. Sometimes. I don't know about any wheel lock. The truck has a auto trans.
JA: Are you fixing your Station yourself? What have you tried so far?
Customer: I took the truck to a mechanic. He said it was a fuse block and he replaced that. It still does the same thing.
JA: Anything else you want the mechanic to know before I connect you?
Customer: I guess thats it.
Submitted: 7 months ago.
Category: GMC
Expert:  Mike S. replied 7 months ago.

Hi, I am Mike, welcome. I'm reviewing your question.

Expert:  Mike S. replied 7 months ago.

Try this. Hold the key on start while you move the shifter from park all the way to low and back and forth a few times while holding the key on start. Does at any time the starter catch?

Customer: replied 7 months ago.
no
Expert:  Mike S. replied 7 months ago.

Ok, that was just a test to see if maybe the neutral switch was the problem.

Is this the Sierra? If so, which engine dies it have in it?

Are you familiar with where the fuse box/s are and specifically the starter relay?

Customer: replied 7 months ago.
I have the 6.6 diesel and the fuse block was has been changed
Customer: replied 7 months ago.
p.s. don't text me i have an old phone
Expert:  Mike S. replied 7 months ago.

I don't text

Go to that underhood fuse block, then tell me if the "IGN A" fuse is not blown.

Customer: replied 7 months ago.
fuse is good
Expert:  Mike S. replied 7 months ago.

If all the fuses are just numbered, than it's #3.

Expert:  Mike S. replied 7 months ago.

Ok, great. Now do you have a voltmeter or at least a 12 volt test light? If so, test both sides of that fuse for voltage with the key off.

Expert:  Mike S. replied 7 months ago.

Then put your finger tips on the starter relay and have someone turn the key to start and tell me if you can feel that relay click.

Customer: replied 7 months ago.
I am sorry. I'm handicaped and I,m in alot of pain. I can't do the things you want me to do
Expert:  Mike S. replied 7 months ago.

Ok, do you want to wait until you have someone to help you?

Customer: replied 7 months ago.
I think I will have it towed in to the dealers. I thought it was a simple fix or at the very least I would have an idea of want I'm dealing with. Thank you
Expert:  Mike S. replied 7 months ago.

Well, you could try this and it should only cost $10 or so. Replace all the fuses associated with that starter and also replace the starter relay. The fuses are that fuse you just checked the IGN A and the IGN C in that same underhood fuse block. Then there is the CRANK fuse in the left I/P fuse block, that is located at the left side of the instrument panel. If it still is doing it, then you may be looking at a faulty park/neutral position switch which is on the transmission. It sounds like that may be it too since you did say sometimes moving the shifter does help it crank over.

Expert:  Mike S. replied 7 months ago.

The crank fuse is #17.

Expert:  Mike S. replied 7 months ago.

Here is the wiring diagram I was looking at,

Customer: replied 7 months ago.
ok thank you. you have been a great help. Have a good day good-by
Expert:  Mike S. replied 7 months ago.

Don't forget to rate me well, so I get credit especially if changing any of those fuses or starter relay does get the starter working, if not, I understand.