03 Yukon - reduced engine power issue

[DonnieBrasco]

2003 Yukon with about 225k miles. Driving down the interstate yesterday and all of a sudden it starts dinging, traction control turns off and it says "reduced engine power" and I can't go over about 20 mph and 2k rpm. Got it towed to my house to try and figure out what's up. I've been reading some about this and have myriad options to look at and was hoping y'all could help me narrow it down before I start throwing money at it. Here are some things I am thinking...

1. Battery and/or alternator. However, the truck still cranks up, power locks, instrument panel, etc. all work. So could I rule out battery and/or alternator just based on that?
2. Throttle body wiring harness and/or sensor. Currently this makes the most sense to me. I've read about people having issues with the wiring harness on the TB. I'm going to open it up tonight and see what it looks like, see if the actual TB is gummed up or if the wires are frayed or anything.
3. Ground for PCM. There's a ground connection for the PCM on the passenger rear of the engine. I've also read about G103 next to the right cylinder head. Are these the same grounds or different?

Outside of those issues, I'm kind of at a loss. It still cranks up, but it's a rough idle (engine shakes more than usual). I don't even know if I can drive it to an auto store to scan the codes.

Disclaimer: I've had an issue for a month or two with my evap purge valve (the one on the engine) but I highly doubt that's the issue that's causing this. Granted, it may have led to whatever is causing this but I don't think that alone is the issue.

 

[01ssreda4]

What code is it throwing? That would help just a tad.

 

[DonnieBrasco]

What code is it throwing? That would help just a tad.

I have no clue. I broke down on the side of the road, got it towed to my house. I *may* be able to drive it to the store this week to run a code scan. But I'm not sure if it'll make it there. Also considering buying my own scanner. Found one on Amazon with good reviews for like 15 bucks. Can I really get a solid scanner for that cheap??

 

[Tonyrodz]

I have no clue. I broke down on the side of the road, got it towed to my house. I *may* be able to drive it to the store this week to run a code scan. But I'm not sure if it'll make it there. Also considering buying my own scanner. Found one on Amazon with good reviews for like 15 bucks. Can I really get a solid scanner for that cheap??

You'll get a scanner that'll be able to read your check engine trouble codes, and maybe clear them out, but that's probably it. I bought one for around $26 online and that's all it does.

 

[DonnieBrasco]

You'll get a scanner that'll be able to read your check engine trouble codes, and maybe clear them out, but that's probably it. I bought one for around $26 online and that's all it does.

What else would I need it to do? As long as I can get the codes I can look them up online, correct?

 

[Tonyrodz]

Yes you can. Mine come with a book that tells you what the codes are, but it's incomplete. I just look them up online, no biggie there. They have more expensive scanners that do a lot more, such as read abs codes, stabilitrak etc, but you're looking at hundreds of dollars more.

 

[TheAutumnWind]

Yes you can. Mine come with a book that tells you what the codes are, but it's incomplete. I just look them up online, no biggie there. They have more expensive scanners that do a lot more, such as read abs codes, stabilitrak etc, but you're looking at hundreds of dollars more.

Just so you know I have a bluedriver https://www.amazon.com/gp/product/B00652G4TS/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 which @ $100 pays for itself after using it once or twice. I can check and clear ABS codes, stabilitrak codes, everything...

 

[Tonyrodz]

Just so you know I have a bluedriver https://www.amazon.com/gp/product/B00652G4TS/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 which @ $100 pays for itself after using it once or twice. I can check and clear ABS codes, stabilitrak codes, everything...

Now that's worth it! Imo.

 

[01ssreda4]

Wanna know a secret? If you clear the code the reduced power will go away! Now that doesnt mean it won't come back but you may be able to isolate how to set it off. Example:not going heavy on the throttle may keep the code from being thrown again.

 

[4WDTRK]

I had this happening every so often. I figured out it only occurred if the throttle pedal accidently got bumped from underneath. It was causing the TPS to go haywire. It always cleared after stopping and shutting off the engine for a minute. Sounds like you may have a different issue though since it's not clearing on its own. Try to get a code and lets go from there.