I have an 06 trailblazer 4.2 L engine. It has had a P0223 code since I got it. After some research I replaced the accelerator pedal(with sensors) and also the throttle body and sensors. That didn't fix it so I checked the signals coming out of the throttle body to the ecm and the readings were 3.6 and 1.5 volts.which I believe are correct at idle.
I also put a scope on sensor 1 and 2 and the signals are very smoth with no "skips". I checked the wires on both sensors to be sure there was no open or ground on them.
I bought a better scanner so I could read the outputs of APP1 APP2 TPS ! and TPS 2 . All readings look good except TPS2 and it stays at 99% except occassionally when I press the accelerator It will drop to a random # like 49% or other # for a very brief instant then right back to 99%. The old and new throttle bodys have the same readings.
I am at a total loss what to next. OH forgot to mention I also replaced the ECM.
I would really appreciate some good advice(other than burning the thing). LOL Thanks for reading

Are the floor mats and carpet in good condition and placed properly?

If so, next step is check for chafed/worn/damaged wiring towards the throttle pedal sensor.

Yes , I checked both of those from standard diagnostic recommendations, I have spent many hours searching the internet for a solution.
however, today the symptoms did change , while reading the output of TPS2 , every 5-15 seconds on my scanner will drop to a random number just for an instant. But most importantly the traction control light on the dash will come on just before or maybe the same time that the limp mode symbol lights up and my TPS2 reading has gone back to 99%. today for the first time occassionally the TPS2 output will read normal for several minuets, all codes will clear and be perfectly fine for 5- 15 minuets.
Suspecting a bad connection somewhere, I drove over some very rough roads but that had no effect.
Tomorrow I will check the con nections on the BCM and possibly after that replace the BCM because I think is involved in the problem because the traction control is ALWAYS involved when TPS2 reads incorrectly. Thank you for your responce.

Do a wiggle test.

The BCM has nothing to do with the fault you have - it'* solely the link between your throttle body and the ECM. Your scan tool readings verify this - the ECM is seeing the voltage from TPS2 go out of range intermittently. Since it'* not constant you may have missed the issue when testing the wiring.

Have you checked terminal tension at the ECM connector? A poor contact there could act just like this, and it happens with these tiny terminals.

dtc assist, Thank you very much for your response. I agree that the BCM is prolly not the culprit. i am just desperate.
I may have not described correctly about being intermittent. My scanner stays at 99% on TPS2 except occassionally a very quick blip to another number , almost to quick to read.(APP1,APP2 and TPS1 all read normal) and I can see all of them at the same time) Reading the voltage on TPS2 , with my dvom (Engine off) I get about 1.45 V (It varys between 1.44 and 1.48. Do you know where I can find out if this is within specs ? That would be a great help.
I have checked throughly for an open or shorted wire or loose connection .
Again thank you very much for your assistance

dtcassist, I can tell you are a very knowledgeable tech and I appreciate your help. I just found the problem. It is a broken connection on conn2 on the ECM.
It is a pin broken beyound where it connects to the wire. That is why when I would back probe it it seemed fine. Thanks for your help.
I will update this thread when I pinpoint it exactly.

That was kind of a slap in the face to the other folks trying to help you out.

I didn't mean to do that. I just wanted to thank every one for their help.... just him especially . I will update the thread when I know the exact problem

ok, I still don't have the problem fixed but I do Have some more info. I borrowed a better scanner so I could see the graph of TPS2. The voltage is up close to 5 v with a "rythmic" spike down every second or 2. It does the same exact thing with 2 different ECM'*.
I have a good 5v. ref to TPS2. I cut (on both ends ) and replaced the TPS2 signal wire and ground. I have from .73 v to 1.45 v reading depending whether the engine is running or not on the ECM conn2 pins36 and 7.
To me this seems impossible but that is what I have and have no idea what to do next.
Any help would be greatly appreciated.