Reduced Engine Power - on startup only

[dukbludvl]

2003 Yukon, 245k miles, 5.3L 2wd -- I started getting the Reduced Engine Power warning a few years ago not long after I bought this truck used from the 1 previous owner. For a year, I occasionally got the REP warning, maybe once every month or so. Then, it seemed to completely go away this spring/summer/early fall. But, once it got cold out, it's come back and is happening now more than ever - probably 5 times a week.

The thing that seems to be different with mine is that it ONLY happens on startup. It never happens with the engine running, at idle, etc.

Is there anyone else out there who's experienced REP with this pattern? If so, what solved this issue for you?

Seems like there are so many things this could be... i hate to start throwing money and parts at it if it's not really going to solve the problem. I know grounds tend to be a big issue. I'm 6'7", 300 pounds, so I'm going to have a helluva time trying to get at those grounds behind the engine at the firewall.

The only other things I might add -- this morning my starter failed. I'm replacing it now. Could a starter going bad be causing these more frequent REP warnings of late?

And the other thing I've noticed is that if I let off the gas in roughly the range of 40-50mph, it seems like the Yukon will just keep going and going, kind of like the accelerator is not adjusting to me not having my foot on it anymore. It slows down eventually, but it takes way longer than normal. Could that be a sign that my issue REALLY IS the throttle position sensor (TPS)?

Thanks in advance for any advice you all can provide.

 

[rockola1971]

You could have butterfly sticking in the throttle body. Check for carbon goop build up. TPS pot wearing out with a dead spot. Throttle pot worn out. It is common for the wiring harness to get a broken wire within the first 10" of the plug that goes into the TPS. If you run your fingers down each wire from the plug you usually can feel the break. *NOTE* It is just the stranded copper conductors of the wire that are broken, not the insulation on the outside. So visually it appears the wire is ok.

 

[Eldiablo]

2003 Yukon, 245k miles, 5.3L 2wd -- I started getting the Reduced Engine Power warning a few years ago not long after I bought this truck used from the 1 previous owner. For a year, I occasionally got the REP warning, maybe once every month or so. Then, it seemed to completely go away this spring/summer/early fall. But, once it got cold out, it's come back and is happening now more than ever - probably 5 times a week.

The thing that seems to be different with mine is that it ONLY happens on startup. It never happens with the engine running, at idle, etc.

Is there anyone else out there who's experienced REP with this pattern? If so, what solved this issue for you?

Seems like there are so many things this could be... i hate to start throwing money and parts at it if it's not really going to solve the problem. I know grounds tend to be a big issue. I'm 6'7", 300 pounds, so I'm going to have a helluva time trying to get at those grounds behind the engine at the firewall.

The only other things I might add -- this morning my starter failed. I'm replacing it now. Could a starter going bad be causing these more frequent REP warnings of late?

And the other thing I've noticed is that if I let off the gas in roughly the range of 40-50mph, it seems like the Yukon will just keep going and going, kind of like the accelerator is not adjusting to me not having my foot on it anymore. It slows down eventually, but it takes way longer than normal. Could that be a sign that my issue REALLY IS the throttle position sensor (TPS)?

Thanks in advance for any advice you all can provide.

check the battery voltage in the morining before start up.

 

[dukbludvl]

No battery issues. I replaced the starter and have not had the REP code since. Seems it was related to the starter going bad.