P2101 and Throttle Body Vibration

[warriormagee]

2007 GMC Yukon XL with 140,*** miles. Two days ago I was driving the truck and it went into Limp mode, with the associated lights and sounds. There was also a very loud sound coming from the engine area. I thought the motor was going to blow. I turned off the truck immediately. There was no smoke and I was in the middle of the street, so I couldn't pop the hood right then. I started the truck again, and the sound was gone, so I drove it in Limp Mode about 50 yards, to a place I could pull over. I shut off the engine and popped the hood. I checked fluid levels, as the truck is known to use oil at a high rate, but everything was good. This all took about 5 minutes. Started the truck up, and power was restored and no extra sounds coming from under the hood, but check engine light is on. Drove it to the nearest shop, about a mile away, and when I turned the truck off, I heard a vibration sound from under the hood. Mechanic checked the error codes and P0171 and P2101 were reported. I told him about the sound under the hood, and when he turned the truck off, he heard the vibration as well. He said that without me putting the truck in the shop for him to go through it, he couldn't tell where it was coming from. I went to his boss with the error codes, and was told that many things could cause the error codes, and we could start by replacing common culprits, but that we would basically have to throw parts at it to see what works. I can't afford to just throw parts at it, so I took the truck home and decided to do some research myself. I was thinking the P2101 error was my base culprit, and replacing the Throttle Position Sensor (TPS) might fix it. I have been driving the truck in the meanwhile, and the vibration sound has gotten a little more noticeable. I had my wife turn the truck on and off, while I was under the hood. The vibration seems to be coming from the throttle body itself. I can place my hand on it and feel the vibration when the truck is turned off. Would a faulty TPS cause this kind of vibration? Does the throttle body need replaced? Any help is appreciated.

***I am in the military, and stationed at a post that is almost 45 minutes from the nearest town. The shop I took it to is the only shop on post. With that in mind, it isn't easy for me to just take it somewhere else.***

 

[goldata81]

I, as well, have been dealing with codes similar to yours, P0121 (throttle circuit performance, P0171 (Lean bank 1) and P0174 (lean bank 2). I believe I have mine fixed for now by cleaning the MAF. However with the codes and description you give, I would suspect the throttle body too as you mentioned. If you have a way of logging OBDII parameters off the link, parameters I'd start looking at would include commanded throttle, pedal position and relative or absolute throttle position. I would expect them to follow each other. If you are unable to get the info off OBDII, throwing parts at it may be your only option besides taking it to a shop. I think I would definitely start with replaceing throttle body assembly. I've attached a plot of a few parameters from my 07' Yukon XL Denali from this morning's drive into work. The spots where the pedal position is flat yet the throttle is still being being moved around is either where the cruise is on or the vehicle is decelerating. Since you say you can feel it vibrating, I am guessing something isn't quite right with it.

 

[warriormagee]

I, as well, have been dealing with codes similar to yours, P0121 (throttle circuit performance, P0171 (Lean bank 1) and P0174 (lean bank 2). I believe I have mine fixed for now by cleaning the MAF. However with the codes and description you give, I would suspect the throttle body too as you mentioned. If you have a way of logging OBDII parameters off the link, parameters I'd start looking at would include commanded throttle, pedal position and relative or absolute throttle position. I would expect them to follow each other. If you are unable to get the info off OBDII, throwing parts at it may be your only option besides taking it to a shop. I think I would definitely start with replaceing throttle body assembly. I've attached a plot of a few parameters from my 07' Yukon XL Denali from this morning's drive into work. The spots where the pedal position is flat yet the throttle is still being being moved around is either where the cruise is on or the vehicle is decelerating. Since you say you can feel it vibrating, I am guessing something isn't quite right with it.
View attachment 69255

Thank you for the reply. Unfortunately, I cannot log OBDII info, as I do not have an OBDII scanner myself. I think I'll replace the throttle body, as there is no good reason for it to be vibrating. I guess my big question now is, did a bad throttle body cause the P2101 error, or did a bad TPS damage the throttle body?

 

[08YUKIE]

I had the P2101 recently and I bought a can of throttle body cleaner, took the intake off the throttle body and used a toothbrush and liberal amount of the cleaner, then had my son with the truck in the on position not running hold the gas pedal down so I could get behind the throttle body flapper. I had so much carbon built up. After that cleaning the truck idled rough but that is part of it relearning the idle. It took maybe 10 miles of driving and the check engine light went off and about a week to get to normal idle, But it only Cost me $4.99 and 30 minutes of my time. Good luck with this.

 

[warriormagee]

So, I removed the intake from the throttle body and cleaned it as 08YUKIE recommended. Before cleaning, I had my wife turn the truck on, and turn it off again quickly. The vibration is coming from the butterfly valve. I cleaned the throttle body, manually moving the butterfly valve, to clean inside it. After driving the truck again, there was no more vibration sounds coming from under the hood. At least for a little while. I used the truck to make short runs (less than 3 miles), about 5 times, before the vibration sounds came back. Can anyone definitively tell me if the throttle body needs replaced?

 

[warriormagee]

Replacing the Throttle Position Sensor has fixed all of the issues in this thread.