Reduced engine power....anyone have a stick of dynamite??

[shegarty]

Hi:

I have a 2004 Yukon xl Denali. Went through same nightmare as you. Changed all these parts and discovered on some forum or YouTube to look at a ground wire behind the engine and ground wires under driver’s side door where it meets the fender. (There are two wires there). I loosened the nuts on all three, cleaned with sand paper and wire brush, sprayed some wd40 and put everything back together. Haven’t had reduced power yet and it’s been almost a year. I felt real dumb that it took that long to fix it but professional mechanics could not fix it either. It worked for me. Hope it works for you. Good luck.

I had the exact same problem and after a bunch of chasing with junk yard parts found that it was as bad engine ground. Pay particular attention to the grounds that run from the ECM to the back of the engine. In my case the wire had corroded at the terminal and then finally broken through which caused a no start condition with all kinds of funky electrical issues. I was unfortunate in that I had to pay shop prices for labour ($1000) to find a 50 cent fix (ring terminal) but I was in the middle of a big renovation on a tight timeline.

 

[tomloans]

John I had those exact codes and I believe it is most often a grounding issue...

See this post and do it. Quit changing out parts for now.

https://www.tahoeyukonforum.com/threads/reduced-engine-power.111769/

After you clean the connection and rewire this ground as noted, unbuckle the battery and put your key in the ignition and turn it to the on position. Then take the key out ( make sure you do this before you connect the battery again). Then buckle up the battery again. You should be good to go then.

 

[tomloans]

Been getting the same codes from the jump P2135 P1515 P0120. The throttle body I changed due to a roughness to the operation by hand I read online of those having and issue with that. The mass air flow sensor my scan tool life feed did show an issue with it being erratic. Yet these same issues continue. During the cold winter's I never have a problem as soon as warm weather starts the issue comes back. That is why I thought maybe the heat was causing some expansion or something in the ECM making for a bad connection or something somewhere. Obviously that was incorrect too. I feel like it's down to the wiring harness somewhere and that is going to be a serious excursion and a lot of time to find and repair I don't have a backup vehicle and can't be down for days or weeks to pinpoint the issue assuming that's the problem. Perhaps trying to find a deal on the tech2 will be worth it. Otherwise I guess it will become a driveway decoration

You have a grounding issue! See my video. Remove the bolt and clean the ground at the driver side firewall carefully ( make the connections nice and shiny with wire brush ) and rewire it like I did in the video ...


https://www.tahoeyukonforum.com/threads/reduced-engine-power.111769/

 

[tomloans]

Here is the video. It solved the problem instantly.

 

[tomloans]

Other than this do one more thing... UNderneath the vehicle drivers side by the front tire, there are two bolts that are also where there are a couple ground wires connected. Take them off and brush the heck out of them and the frame where it is connected. Often the spray on rubber stuff is blocking a clean connection. take care of this too. Let me know if it works for you too. The two items resolved my issue instantly. I think the main issue was the the cable at the firewall but take care of this too and you should be good to go.

 

[John Bragg]

Awesome info and very easy and cheap I'm going to do the new grounds immediately and definitely clean the hell out of them great video very helpful and great idea. Thanks much appreciated

 

[tomloans]

This is what it looks like in the back. These are the two that are hard to reach and hence I have bypassed one and plan on bypassing the other. I think in my case the passenger side is fine for now only because when this one loses contact, you have more indications over and above just the a 1516, 2135, 0220, etc... All kinds of issues arise when the passenger side loses contact.

 

[tomloans]

Here is my other post which has additional items in it.

https://www.tahoeyukonforum.com/threads/reduced-engine-power.111773/

 

[John Bragg]

Hey Tom do you recall the bolt and thread size that went into the block?

 

[tomloans]

let me check stand by