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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 29427
Experience:  GM Grand Master Technician 2007. 14 year experience.
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I have a 03 gmc 2500hd 6.0 When ever I get on the gas to

Customer Question

I have a 03 gmc 2500hd 6.0
When ever I get on the gas to enter the highway the truck boggs down says "reduced power" and check engine light comes on. If I turn the truck off for 30 secs. I can get my power back, but the check engine light stays on. Last time the engine light stayed on for about a day it drove fine. Then all of a sudden it happened again. This time I took it to get the codes. At this time it was not in limp mode I had to restarted it. The truck came back with 16 codes most dealing with ground to battery.
Submitted: 10 months ago.
Category: GMC
Expert:  Gm Tech (Cam) replied 10 months ago.

Hi there, I am Cam.
Can I get your first name please?
I am not sure if you have used our service before or not. The experts here are third party contractors. Myself, I am a GM technician in a Gm dealership. I will be happy to help you. Please understand that my only compensation for the time spent helping you is by your rating of my service in a positive way. The more information you provide, the better the chances of getting your issue resolved. Also please reply if you have any followup questions.
So about your vehicle,

These years of trucks with the electric throttle have a couple of very common issues. First and in my experience most common is the ground wire. THe ground runs from the rear harness behind the top of the engine to the rear of the left cylinder head. It is attached at the same bolt as the ground strap at the firewall. I have always been able to find this by pulling on the black wire and see if it gives. The fault has been a conductor broken in the insulation at the crimp. The second issue is the wiring near the throttle body. The wiring tends to break a few inches from the connector. check these out and see. Another common issue is the wiring near the throttle body itself. There are some wires there that can break inside the insulation and cause this. Check the wiring carefully near the throttle and about 6" back.
Also check the wiring at the pedal under the dash, micro corrosion in the connectors can cause issues and even unplugging and plugging the connector back in will correct, it so then put some electronics grease on the pins. Finally is a connector in the throttle body itself. It is common for the pins in the connector to fail and cause codes. The repair for this is the pigtail connector for that throttle body.

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