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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 29520
Experience:  GM Grand Master Technician 2007. 14 year experience.
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Hummer H2: reduced engine power on 04 hummer h2

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reduced engine power on 04 hummer h2
Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.Often this is a ground wire at the back of the drivers side cylinder head. This ground attaches at the same spot as the braided ground strap. Try pulling the black wire to see if it gives. If so then replace the terminal end. IF not then look to bad wiring at the throttle body. These are also common for bad wiring at the plug or near it so checking the plug and wires there may find the issue. If these don't work then can you get the codes from the system?
Customer: replied 5 years ago.
hey cam, heres the situation, my 04 hummer was working 100% fine before installing a Hummer/GM certified offroad light kit....made specifically for this vehicle...the only things touched was the ground mounting spot and the trailer brake harness under the fuse box under the hood. i started the vehicle and after 10 seconds it bogs down and says reduced engine power....

i then disconnected the harness for the offroad lights completely, undoing the ground harness and reattaching the trailer brake connection just like it was before i started. and it still shows this reduced engine power condition.

if i put the hummer in reverse...the engine dies instantly.

i know its something that ive done, but ive went back and forth over my steps 100 times in the last 3 clueless
Ok, check the connectors under the dash for the pedal. Take them off, clean then and put then back on. If that does not then can you get me a code number?
Customer: replied 5 years ago.
nothing was done inside the vehicle at all, this was all under the hood work! i have no way of moving the vehicle now at all
Ok, if all the grounds are good then try a reset. ke the battery cables off, touch the ends together for 10 seconds then put them on the battery to reset the vehicle.
Customer: replied 5 years ago.
did the battery disconnect and recleaned my ground, still nothing, just goes to reduced engine power after a couple seconds of starting
Ok where exactly was the ground who's touched?
Customer: replied 5 years ago.
the ground has a couple more wires attached to it already...on the frame in front of the driver front wheel
Ok, can you take them off and clean to bare metal. Second take the grounds under the drivers door off and clean them.
Gm Tech (Cam) and 2 other GMC Specialists are ready to help you
Customer: replied 5 years ago.
hey dude, i have fixed wasnt a ground issue at all. under the hood in front of the driver the fuse box there....the problem was when i put the surrounding cover back on..i was pinching some wires off.

when i started the hummer without the cover fastened it ran fine, once i put the cover back on a second coded i took the cover back off...and it was fine once i put the cover on very very carefully (taking like 10 minutes), making sure all grooves and fasteners were hit 100% correctly...and it ran fine....i took it on aXXXXXaround the neighborhood area....and at times opening up the throttle, and no problems whatsoever! so my problem was simply that cover pinching stuff off.

your help and input was greatly appreciated! especially without seeing the problem first hand!