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Won't rev past 2000 rpms

I have a 2007 GMC Sierra classic 5.3 4x4 when I go to drive it won’t rev past 2000 rpms until I reach 50 mph then it will go to 2500 rpms when I put the gas pedal to the floor its the same 2000 rpms

How many miles on this? Is the check engine light on? Is it flashing? Do you know the error codes it is setting? For how long? How long has it been doing this? Have there been services recently?

213xxx miles no engine light on or flashing
Took it to a tranny shop they didn’t know what was wrong with it. My grandpa just fixed all the codes the shop had put on it after not putting the wires back on it it just started doing this last week I drove it home no problem the next morning is when it started not going above 2000 rpms no codes are thrown I’ll check again today after work though

After I got it from the shop they had my abs light on service brake system display on an my speedometer wasn’t working also they put a metal clip in my transmission pan an didn’t fill it up with transmission fluid all that was fixed on Sunday it still doing the same thing when i drive it though no lights are coming on. Just not reving above 2000 rpms even when I floor it…

Have the spark plugs ever been replaced?

I also wonder if you might have an exhaust problem, like a plugged catalytic converter. But I’d expect you to have a code for that.

I have not put any new spark plugs on it I’ll see if they need replaced as for the plugged cat I haven’t check that yet

That does not make sense . He fixed codes ? No the shop did not put codes on it. Somehow I think you need to find a better shop and it will cost you about 125.00 to find out what the real problem is .

Yeah that’s what I was getting at they didn’t plug my wires back left em hanging please stay off this if your not giving me help lol

Sounds to me like it might be in “reduced power mode”, especially considering it was driven without the wiring to the transmission electronic controls hooked up (if I understood that right). One thing you might try if there is no check engine light on, is resetting the computer by pulling the battery cables and touching them together. If the check engine light is on, do not reset the computer, get the codes read instead.

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Ok thanks John I will try that