'05 Chevy TB EXT
Thanks ... let me see if I can figger the white text out ..... I hope my post is better now .....If I'm at 20mph and floor it while the selector is in 2 it will downshift...
Also your reply is in white text
Ok ... now on to the 2nd gear thingy .......
When you manually put the gearshift in2nd/intermediate position ... it must stay in 2nd gear/intermediate, no matter what throttle position application you use. Without modifications, that is a designed-in default by the engineers.
I suspect there's more story here that we're not hearing.
At any rate ... gently rolling along at 20 MPH in OD, you might be in 2nd/Intermediate and adding throttle might create a "should I - shouldn't I" momentary confusion by the TCM-slash-transmission as to whether it should drop to 1st or just hang on because the TPS isn't reporting any wild throttle use yet.
That scenario could point to a bad TPS, but we all know of the dreaded REP and P2122! ...... so we might be able to drop that line of thought early on.
The same with a bad/defective VSS ... for pretty much the same reasons (SEL and non-OP cruise control, etc) ... so unless you've got some 'splaining to do, we'll drop that line too ...........
There COULD be a hung 2-1 shift solenoid-sequencing problem .... but the ECM watches the TCM and THAT ain't gonna fly under the radar without an SES too.
There MIGHT be some ungodly high line pressure that's blocking a shuttle-to-1st .... but that's unsubstantiated because there isnt or hasn't been any other transmission idiosyncrasies noted by you ..... so far.
Dirty solenoid? Uhmmm .... perhaps .... mebee not.......
Dirty throttle body? Don't EVEN go there!
We need more input.