TPS issue and Dealer

Hello Everyone and hope everyone is doing well ? I don't usually post here because auto mechanics is a complicated subject for me but I love reading the solutions, suggestions and critics here. My 2011 Chevy Tahoe LTZ 5.3 has behaved flawlessly since day one (13 years ago). I had a 2003 Tahoe previously for many years. We have driven cross country, up and down the east coast, ventured as far north as Quebec during our skiing trips and all the way to Austin, Texas. I kept going to the dealer religiously for preventative maintenance, all the way up until the warranty expired and then to my local mechanic who is a long time friend. The car has been maintained beautifully both mechanically and cosmetically without any accidents and I am currently at 171,350 miles. Oil changed in October and tires only have 25K on them.

Veterans Day weekend, the wife, the dog and I drove up to Richmond, VA (282 mile trip) to participate in Veterans ceremony from my old Army command. The day we arrived, my check engine light turned on and I took it to Auto Zone. They showed me that the code read: P0121 - Throttle Position Sensor (Repair Immediately) which I did . Once they replaced the TPS the truck ran prefect and we drove back to NY, four days later without issues.
Fast Forward to this Monday, Dec 2nd - the truck began to give me a hard time when starting it in the morning. It would crank, continue to crank but not turn on. After about 3 tries and pushing down on the accelerator, it would rev up high, turn on and then lower itself to normal rpm's. It kept running perfect the entire day, except when I turned it off and on again. I took it to my mechanic the following day. He looked it over and called me to say that he thought "I should take it to the dealer", since he did not have the proper diagnostic machine to determine why it was doing this as he had replaced the fuel pump 4 months prior. On Wednesday, without a appointment, I go to the Chevy dealer here in Nassau County at 7:30 AM, wait in line and speak to the service folks and leave the truck after explaining the past few days events. They quoted me $269. for the Diagnostic Test alone.........Come that afternoon, they call me to tell me they could not get to it because they were busy with the scheduled appointments and that they would call me Thursday. On Thursday, they called me in the afternoon to tell me they had not looked at it but they would call me Friday. Well, they called me Friday at about 1:30 PM to tell me that the specialist would not be able to look at the truck until Monday. Today, Saturday, I went to the dealer because I had left my office keys in the center console which I needed for Monday and the truck was in the yard. NOW, do you think they are that legitimately busy (the place was packed with cars in the bay today and a full customer waiting area) or am I being prepped for a major $$$ hit ?

AND of course, I looked in the dealer lot and the newer Tahoe's are calling my name.....ahhhhhhhhhhh

Moved you here from the 2021+ section.

Sounds like a VENT VALVE or PURGE VALVE issue. Google them and or use the search function here.

Failure of these 2 EVAP system parts is likely to occur if you don't stop pumping gas at first click when filling up. They are not expensive or difficult to install. They can also fail due to old age too.

Did your mechanic actually check fuel pressures or just assume that since he replaced the fuel pump, it can’t be that?

Many dealers are short staffed and getting slammed right now with people getting ready for holiday travel so I’m not surprised that they couldn’t fit in a “walk-in” job. Our local dealer is booking a week to two weeks out right now.

Thank you for clarifying the dealer situation. I will let everyone know what the issue is hooefully really soon

the tb you replaced, was it from autozone?

we have seen a rash of bad parts. might just be you need a oem replacement tb.


I think there's also a idle learn or something like that for when you change throttle body's. they was a post around here somewhere a few months back.

Good Evening Everyone......I finally picked up my truck this afternoon at the dealer. They have been backed up and after 7 days called to tell me that the cause of my problem was: My battery (4 years old ) and my mass air flow sensor. They reprogrammed everything to include Throttle relearn/cleaning, and went through the truck with diagnostic testing. Glad to report that she is otherwise in very good shape both mechanically and body wise $ 634. 00 later................Oh well but the increase in engine power is like night and day.

Thank you All and have a safe and wonderful Holiday Season !!!

Great to hear you got your truck all squared away.

And, a big thank you for your service.

The honor was all mine

Folks, I am back with some much needed advise. In my original posting, I described the issue of that my Check Engine light went on after a long drive from NY to Richmond, Va and was diagnose at Auto Zone as a P0121 - Throttle Position Sensor., which was replaced. Came back home worked perfectly for about a week, then the truck started giving me issue when starting. Under advisement from my long time mechanic, I took it to the Chevy dealer and got it back 7 days later because they were so backlogged. They replaced the battery, Sensor, performed throttle relearn procedure, cleaned the throttle body, performed the G.M. multi point inspection and still the RPM's go from 1500 to 400 and then levels out on initial start up. The last 2 days our temp has been in the teens here and the truck give me an extreme hard time to crank up. I have owned it since new and it never has done this before or given me any major issues like this. It is NOT showing Any trouble or Engine light and on the repair sheet it says NO TROUBLE CODES STORED. I called up the dealer and they suggested that I change the Mass Air flow Sensor since they were back ordered on it, which I then did. but no noticeable change in idle and start up.
Truth of the matter is that since I am not mechanically versed, I am looking to repair this issue and sell it/trade it and move on with a newer Truck.......................ANYONE have any ideas on why the dealer cannot come up with a solution.