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Ron, ASE Certified Technician
Category: GMC
Satisfied Customers: 35642
Experience:  35 years in the Automotive repair business.
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I have a '95 3500 gmc dually (89k miles)that the trans went

Customer Question

I have a '95 3500 gmc dually (89k miles)that the trans went into limp mode. After doing some checking and reading I came to the conclusion it was actually my ignition switch causing this. I could un hook the bat/reset and the trans would work fine. When I turned off the truck it would sometimes run for another second or so. This is when it would go into limp mode. When the truck cuts off immediately it does not go into limp mode. So, I have changed out the switch/harness a couple of times and the truck will still run on when switched off. This of course kicks it back into limp mode. The CEL does not come on so I haven't check for an actual code. Has anyone else heard of this or know what I should do? Thanks for the help
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Submitted: 1 year ago.
Category: GMC
Expert:  Ron replied 1 year ago.

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.

If you are sure the system is going into limp mode then in most cases the computer would be setting a fault code and or codes, I would go ahead and scan the computer system and see if there are any setting even if the light is not coming on. If you can get this done and post back with the results I will try and help you get this resolved.

Customer: replied 1 year ago.
Thanks for the response. It will be next week. Going out of town for the weekend. I will report back with whatever codes I get.
Expert:  Ron replied 1 year ago.

Not problem, post back when you can and we can work from there.

Customer: replied 1 year ago.
Sorry to drag this out. I'll be in touch soon
Expert:  Ron replied 1 year ago.

Not a problem, let me know and we can work from there.

Customer: replied 1 year ago.
I finally got a scanner on the truck. It has no codes faulting or any codes stored. I have put a brand new ac/delco switch harness in and it still will run on and throw the trans into limp mode/second gear. the selector reads the correct gear on the scanner. once again if you unhook the battery it shifts fine.
Customer: replied 1 year ago.
It does not always run after you switch it off. It only goes into limp when it runs on
Expert:  Ron replied 1 year ago.

Unfortunately with out having a fault code and something to go on I'm not sure I can advise you on the proper fix from here. I'm afraid this is going to require some hands on help. I can open the post back up if you would like in hopes someone else may have some other ideas.

Customer: replied 1 year ago.
please, I didn't pay $29 for nothing :)
Expert:  Ron replied 1 year ago.

You are only charged once you rate the service , any money you have placed in your account remains your until then. I have relisted the question for you. If someone can help, they will respond.

Customer: replied 1 year ago.
Ok , thanks Sorry it took so long to get back,
Have a good weekend

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