2003 Yukon Reduced Engine Power

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S33k3r

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On our 2005 Suburban 2500, we had water intrusion at/near the ECM. The ECM itself was okay, but the wires leading to it had corroded, cracked, and some were broken.
My wife drove through water up to her wheel wells; It took us 6 weeks and 2 mechanics to get it sorted out. But a friend recommended a local mechanic; he figured it out, fixed it, explained it to me, and didn't charge me the arm and a leg it SHOULD have cost to track down this electrical demon.

My wife and daughter just got back from a round trip to Mississippi in it.
 
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Tatman71

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Ok. Replaced the throttle body wiring harness. Also replaced the T.A.C. module.. Seen the date on my battery of 8/16. So just to make sure I replaced the battery. Still will not come out of reduced power mode.
To recap. Plugs and wires were changed. Still random miss fire. All coils were replaced. Random miss fire fixed. Still going in reduced power mode. Codes pointed towards tps and/or foot pedal sensor. Replaced throttle body, tps and foot pedal sensor. Still reduced power mode. Upon advice I checked and replaced tps wiring harness. Still in reduced power mode. Also upon advice replaced the T.A.C. MODULE and battery today. Still in reduced power mode.
Attached is a picture of the codes still being thrown. Not sure whats next.
 

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tomloans

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Super important that when you replaced the wiring harness, you solder the connections - this is a must. Again this is a must. Do not use crimp connectors or solder connectors of any kind. This is must do.
The two grounds behind your engine can be the issues as well. There is a thin ground wire that will often break on the passenger side of the back of the engine. Be sure that is corrosion free and not broken off. There is a ground strap bolted to the fire wall and the back of the engine on the driver side. The firewall connection is usually corroded - you can't tell by looking at it. Take it off and brush it and the firewall contact point as well. You will see white dust coming off of it. Reattach after cleaning. Under the passenger side under the carriage you will find 3 grounds attached to the frame. Remove the screw/bolt and brush thoroughly each wire connection and both sides of the frame until you see shiny metal. GM coated the metal then attached the grounds ( great move!). Finally and again I repeat, the wiring harness needs to be soldered and then use shrink tubing to cover them. I can't be more emphatic about this. Also be very careful as you can easily make another break when manipulating the old wiring. Remember the heat and vibration caused the break. This means is can easily break somewhere else along the lines as you are messing with them. Be careful.
Also you mentioned that the reduced engine power hasn't gone away. Has the symptoms changed at all while replacing parts or has it been exactly the same? Some time like in my case, one part would solve the problem for a few years and then I would have another issue but the way reduced engine power would rear its' ugly head was different. For instance this last episode was only during idling or first start up.

You are not alone. Don't give up... Read the comments as well

 

OR VietVet

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Yea, that TPS harness is recommended in the different TPS choices at RA. Well known problem and RA gives the harness part # with the TPS part #.

Suggestion, the PCM is mounted next to your battery and is really kind of hanging out there. I recently sent mine in for a tune at BBP and I saw how exposed it is. I was very careful to clean and inspect before I re-installed it. The TPS harness should be soldered as @tomloans said, but for now, I would assume you would not have the exact same problem if you butt connected them when you did yours.

For S*H*I*T*S and giggles, do you have good exhaust flow, so you can rule out a clogged exhaust? Low % of that being the problem but if I experience any loss of power I always do 3 things: check exhaust flow, check fuel pressure and check for a binding brake. With the codes you got, I doubt either is the problem but I am a*n*a*l about crap like that.

Welcome to the forum.
 

OR VietVet

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Isn't that kind of why you are a good mechanic? you left no stone unturned when you were trouble-shooting?

It has been my experience that when something is skipped because "that can't be the problem" that you find out that was the problem.
Sometimes there is no excuse for "tunnel vision" when you are supposed to be an open minded tech. To this day, I still work on the side. I ask so many questions about a problem, that I have independent people say, "I have never been asked so many questions". I am in the running for a service manager job here locally. I love running shops.
 

S33k3r

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Sometimes there is no excuse for "tunnel vision" when you are supposed to be an open minded tech. To this day, I still work on the side. I ask so many questions about a problem, that I have independent people say, "I have never been asked so many questions". I am in the running for a service manager job here locally. I love running shops.
If we vote for you, can we get any discounts? :Big Laugh:
 

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