jvmorgan

First off 2007 Silverado 4.8L 4L60E was showing the codes P0174 - system too lean bank 2 and P0171 - system too lean bank 1 and a P0121 Throttle/Pedal Position sensor A circuit. The P0121 has only shown up once.

So I am having the typical problems associated with a dirty throttle body/TPS sensor of the tranny shifting very hard into all gears. So after research about the TPS sensor i found a dirty throttle body could cause this condition because of the drive by wire and the sensor being dirty. So I remove it carefully and clean the sensor with some throttle body cleaner from CRC and I also clean the MAF with the CRC at the same time. No problem I let them dry out for about an hour and re-install. I clear all of the check engine issues and when is start up no problem at all just a little higher rev then normal. So I take it for a test spin and I find that the rev issue is now allowing me to take the foot of the accelerator and there is no de-acceleration going up hill....so I get back home and put it in neutral and it revs up to around 2 to 2500 rpm and I shut it off because it is going higher.

My worst fear is that the TPS is shot and I am going to have to buy a new throttle body. Since the sensor is sold as 1 piece with a new throttle body. Any idea's besides possibly it was not dried out even though it is alcohol based and should evaporate after an hour of sitting?

Thanks
Justin

kc'skustom95

I had the P0121 code in mine so I took the throttle body off then ported and polished it. I then had the same issue you mentioned. At this point you must do one of two things:

1. Take the truck to a dealer so they can perform a "TB relearn proccedure" or what I did,

2. Dive the truck at least 250 miles at 60 MPH and it will relearn it self. Then you can clear the codes and everything is fine.

I have a 70 mile round trip commute every day so the second choice was no problem for me.

BigD50

I have a 04 yukon SLE 5.3 flex fuel...About a month ago I replaced the air filter, took of the air intake tubing that leads to the throttle body. I then clean the throttle body with TB cleaner and the MAF sensor with MAF sensor cleaner...also had my oil changed a few days ago at a shop b/c I didn't have time.

I am now getting the P0171 (two of these) and P0174 codes...I have 150,000 miles and never repalced the 02 Sensors...Is this same issue as above? Odd to me the sensors would go bad at the same moment.

BigD50

Found this...
Smoke testing for codes P0171 P0174 - YouTube

BigD50

Dealer confirmed, it is my intake manifold gasket. They said 50/50 shot that just a gasket replacement will fix the issue since the intake manifold can warp...I think I am going to try to just replace the intake manifold gasket with the new redesigned one, and use new bolts to hold down the gasket...I think that will do the trick.