OK me and my tuner are at wits end. We are working on an ls6 from a 2004 CTS-V.

We have got all the codes to clear or we do not get any codes period but the throttle body oscillates. All the data on the TECH II is within range and agree as they are suppose to. The car will crank and run but once you start giving it pedal or trying to hold the pedal at a constant RPM the TB starts moving all over the place and when you drive it and give it pedal at above 40% it feel likes it is cutting out but its the TB oscillating you can see it on the TECH II. We checked for a vacuum and did not find one, also the TB will do it without the engine running so that should rule out a vacuum problem, When you turn the key on the TB does it click and it fine, but if you depress the pedal with the engine not running and the key on the TB starts moving all over the place, it sound like you are typing Morris code. The volts on the TB motor both 1 & 2 move from 12.60 to 12.40 when you depress the pedal 100%. We have changed the TAC module, APP sensor twice, TP Sensor tried 4, Throttle Body times 3, New TAC module plug, New APP plug, new wiring between the TAC and APP, New Throttle Body plug,. My turner has a Vette and we can verify that the parts that inter change work on his car and still we get the same osculation on mine. We completely remove all the tape from the harness and check all the wiring, every thing ohms ok. Check the ground from the TAC, even cut the pink wire for power from the ignition to the TAC and wired it straight to battery terminal to check and see if we very losing voltage somehow, nothing we have done will make it stop. We have move the wires on all the connectors while watching the DMM, nothing and change some of the plugs. Bob can take control of the circuit with the TECH II and increase the RPMS and it runs smooth with no osculating. That why we felt like it was in the APP sensors even though they all read ok on the TECH II so I bought a 2nd one but we still got the same thing. Bob thinks that is has got to be the TAC Module and based on everything I think he may be right but we have already bought a new and its on the car the other one I have already sent back for the credit. I guess its possible that we got a bad one. Bob has over 400 tunes under his belt and this one is kicking our tails. He cant tune it if the TB is acting a fool.

Before the common code was P0220 and P2125. By the way The GM Service manual has the drawing wrong for the APP plug. It took some work but we have it wired like it should be as all the sensors are reading correctly on the TECH II.
I have a drawing that I can email you but I can't get it to attach here.

You got any thoughts on what we may have missed

 

bump any one

 

This link gives a pretty accurate description of the APP/TAC circuit that may help narrow down your hiccup.

http://www.gearchatter.com/viewpost14722.php

 

I think your idle is unstable and the throttle is what has
the role of stabilizing it, by jumping around. You see the
same thing on cable throttle cars when the mixture is too
fat or things are not set up right after mods. Loop stability.

I'd begin with the idle mixture (indicated stoich on a modded
car, being not necessarily the right answer for real in-hole
mixture or best idle) and the advance / adaptive spark.

 

You trying to tune it with a TECH II? What are the mods? And you say that it's from an 04 CTSV, is that what it's still in?