Reduced Engine Power

Paulie G · February 3, 2011

My Dad is having some problems with his 03, 6.0. Wondering if any of you guys can help him out before he wraps it around a tree.

"I have the Reduced Engine Power light going off all the time on my 2003 HD Chevy pickup, a friend of mine checked it out and its shows up as a P1516 code. It never did this until I changed out the water pump gaskets, the only wires that would have come in to play changing gaskets are the ones on the air cleaner. After changing the gaskets I believe it was the same day it started quitting on me, at that time I thought it was an air pocket in the coolant that made it do that, the light would come on and it would go to reduced engine power, I got out and burped the upper radiator hose and the check engine light would go off. I was told that the check engine light should stay on until the truck is started so many times or it’s hooked to a programmer and shut off.

Things I have tried are (1) cleaned the throttle body with throttle body cleaner (2) cleaned and bent all the wire connections on the plug going in to the air cleaner. (3) cleaned the ground cable from the hood to the firewall and run a new one along side it (I’m not sure why there’s a ground cable there when there’s no light under the hood) and the ground on the fire to the motor, I didn’t get the one on the back of the motor but I did run a new ground from the firewall to the motor, so I have two new grounds run so far. (4) We checked the yellow wire on the throttle body and that checked out fine.

It’s getting (reduced engine power) and now all I have to do to get the check engine light to go off is open the hood, it won’t go off on the first safety latch it when I open it all the way and I don’t have to open it fast I can open it as slow as I can and it will still make the check engine light go off. If by a 1 in 10 chance that doesn’t do it all I do is wiggle the ground wires and it will go off. The meter does show a discrepancy between the foot feet and the throttle body like some of you have mentioned and it seems like I can feel it when I’m driving once and a while but that could be in my head after reading it.

I can’t see taking it to a dealer and finding out $3000.00 later they don’t know what it was so they replaced everything, I’ve asked a couple dealers I know well and they don’t have an answer. "

Thanks in advance

SouthCo · February 3, 2011

Reduced engine power on the DIC and check engine light was coming on almost daily on my '03 Tahoe. Took it to my shop (not a dealer) and it ended up needing a throttle position sensor. They replaced the the throttle body (because it and the throttle position sensor are one unit) and it has run great since (about 5 months).

Not saying that's your problem.

cliobogger · February 4, 2011

id go with the throttle position sensor as well. thats what it sounds like to me.

ChevyTech77 · February 4, 2011

Throttle body or a wiring issue to the throttle body. Seen a bunch of both.

txab · February 4, 2011

Throttle body or a wiring issue to the throttle body. Seen a bunch of both.

+1

cdn111 · February 4, 2011

check the wires that plug into the throttle body. I beleive it was a yellow wire about 6" back tends to be crimped/broke. You have to pull the plastic off and thoroughly check wires to find it.

Paulie G · February 6, 2011

Does the yellow wire go directly from point A to point B so that it could be completely replaced. Or does this wire make a few junctions along the way?