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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1693
Experience:  GM Grand Master Technician 2007. 14 year experience.
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My 2003 GMC c4500 speedo says that I am going 85, but im at

Customer Question

my 2003 GMC c4500 speedo says that I am going 85, but im at about 35.
JA: What is the model of your '03 GMC?
Customer: likely a Topkick
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: I will be. I just dont really have an idea where to start. Im pretty clueless on electrical
JA: Have you checked the battery, particularly the terminal connections? Are they corroded?
Customer: No. I just put brand new batteries in about 2 months ago.
JA: Anything else you want the mechanic to know before I connect you?
Customer: It started after I used it to jump start another truck.
Submitted: 1 month ago.
Category: GMC
Expert:  david craig replied 1 month ago.

Hi Im David, thanks for visiting the site. disconnect the negative battery cable for 10 seconds. reconnect it, turn the key on, make sure the speedo does a good sweep then see if that takes care of the issue

Expert:  david craig replied 1 month ago.

are you there?