2003 GMC Yukon DTC codes

Tiny
FLYNNHART1
  • MEMBER
  • 2003 GMC YUKON
  • 54,000 MILES
Hi Guys,
I removed my truck's throttle body to clean it and after reinstalling it the Reduced Engine Power light came on and the truck would only idle. I had no throttle response at all. I have a code reader and I got P120, P220, P1516, and P1518. After doing a lot of research I found that these DTC's are a pretty common issue with GM trucks. The P120 and P220 codes point to the TP 1&2 sensors and the P1516 and P1518 seem to point to wiring harness issues. I found information on how to test the TB (Voltage and Resistance measurements) and all measurement seem OK.

I checked the wires on the connector that plugs into the TB and found no broken wires (another common issue with GM) I wiggled the harnesses and nothing changed.

I have checked all the ground associated with this (especially S103) and they are tight. Battery is brand new.

I have found that I can clear the DTC's, and without starting the engine, shut off the ignition, turn the ignition back on (without starting the engine) and all 5 of the above mentioned DTC's will appear. I have also found that I can clear the DTC's and then start the truck and if I give it gas right away I get normal throttle response and as long as I keep it above 1000RPM's it runs normal. As soon as I let it idle the REP light comes back on and all 5 of the DTC's are present. I have done this process 3 times and got the same results each time.

I found that the 5V Reference to TP Sensor 1&2 goes to 0V (one or the other, not both) most of the time when I get the DTC's. Grounding either of these wires will cause them to go to 0V. Turning the ignition off and then back on will reset them to 5V.

From what I have read there have been cases where GM itself admitted to not knowing root cause. I've read horror stories about folks that have spent thousands of dollars and still have this problem.

I would be great if you could give me some advise as to what the problem might be, I would really appreciate any time you could give me.

Thank you very much,
Robert
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Thursday, September 5th, 2013 AT 11:08 PM

6 Replies

Tiny
CADIEMAN
  • MEMBER
Does it seem to run rich? Have you tried spraying carb. Cleaner in the throttle body to see if it will rev up? What is the vacuum reading? Your going to need the trouble trees for each one of these codes and thats in the factory shop manual.
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Friday, September 6th, 2013 AT 12:46 AM
Tiny
WRENCHTECH
  • EXPERT
It seems that you are trying to look at this as a factory defect when in reality it appears that you simply damaged the electronic throttle body which never should have been removed to clean it in the first place.
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Friday, September 6th, 2013 AT 2:57 AM
Tiny
FLYNNHART1
  • MEMBER
Hi Wrenchtech,
I m certainly not trying to imply it s a factory defect, just that it is common and hopefully because of that, someone knows how to fix it (there are 569 posts on Edmunds. Com from people with this problem). It seems that a lot of dealerships are having trouble identifying and fixing this. I agree I shouldn t have removed the TB, however, that is in hindsight. It just seems strange that by just removing the TB and spraying it with TB specific cleaner and reinstalling it would damage it. That being said, if I did indeed damage it, I don t mind buying a new one, I just don t want to go about fixing this problem by going down the shot gun process. I was looking for someone to tell me what they thought the problem most likely is. From the DTC s it appears that the problem could be the TB itself, or the harness/connector. The connector seemed likely because of my removing it from the TB but I checked it for opens/shorts and found none.

Hi cadieman,
If I clear the DTC s the car will start and rev just fine. It will rev up and down and run fine at all RPMs as long as I keep it above 1000 RPMs or so. As soon as I let off on the pedal it goes to 600 RPMs and them after a couple of seconds it goes to 1200 RPMs and stays there. The engine will not respond to any more throttle movement at this point. REP light is also on. I get the same DTC s every time this happens. I have tried this process several times and always get the same results.

Can anyone tell me if a bad TB could set off ALL of the DTC s I m getting, especially the P1516 and P1518?

Thanks
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Friday, September 6th, 2013 AT 2:46 PM
Tiny
WRENCHTECH
  • EXPERT
Nobody is going to know exactly where the problem is without extensive testing. You're getting codes for both TPS and the throttle control module and it's communication line. Just the fact that this happened after you removed the throttle body and sprayed it with chemicals that you shouldn't have really point to a damaged throttle body but who knows for sure without testing. I think you just made a very expensive mistake.
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Friday, September 6th, 2013 AT 3:06 PM
Tiny
FLYNNHART1
  • MEMBER
Hi Wrenchtech,

"you are trying to look at this as a factory defect
"which never should have been removed to clean it in the first place
"you removed the throttle body and sprayed it with chemicals that you shouldn't have
"I think you just made a very expensive mistake

I guess I was looking more for help than criticism. Thanks anyway.
Flynnhart1

BTY - I have done quite a bit of testing already, only a portion of which is in my first post. I am a member of Alldata and and so far all I have performed all of the recommended diagnostics and troubleshooting called out in the DTC and TSB sections. All tests have passed so far.
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Friday, September 6th, 2013 AT 7:26 PM
Tiny
CADIEMAN
  • MEMBER
Ii would go to the salvage yard, pull one and install it. Unless you have the money to buy a new one with all the sensors and then you will need to properly check all the codes per the manual. Wrenchtech is right you have a headache on your hands. Your probably are going to need a veteran master tech. To fix it. We cant do it over this site.
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Friday, September 6th, 2013 AT 7:30 PM

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