Cadillac Repair: 96 Eldorado overdrive, message validation, validation error

Question
I have a ’96 Eldorado (97k miles) and my transmission is acting up. When the car is cold it will shift into overdrive but only stays there for a few minutes, once the car is up to temp, it shifts into overdrive for less than a second then back to 3rd gear and stays there, it always shifts at 41 mph unless you really have your foot in it.
The RPM’s drop down when coasting, but if you put the car in neutral when coasting it feels like something is locking up in the tranny for a half second before it gets into neutral.
The tranny fluid level is OK when hot.
A few weeks ago it was below 0° and the car seemed like the engine was missing at idle then again when it shifted into overdrive, as speed picked up the bucking and missing went away.

No engine codes were displayed, when this problem was happening.

I’ve had this car for about 6 months and don’t know any other history.

I did jack up the idle since the engine would kill at stop signs causing an occasional idle control error.

Engine codes:

PC0507
No IPC
No ACM
No SDM
No TCS
No RSS
No PZM
No IRC
RF2650
No COT

Any suggestions?

Thanks,
John  

Answer
NEVER jack up the idle speed as this causes problems with sensor inputs to the computer. The stalling is in most cases caused by a blackish residue buildup within the throttle body and on both sides of the throttle plate that needs to be cleaned off using an aerosol type cleaning agent availbale at any auto parts store.

PC0507 = Idle speed higher than expected due to your raising the idle speed.

RF2650 = Message validation error.

You need to clean the throttle body as stated above and get the idle back down where it belongs and then CLEAR (erase) the 2 codes from the computer via the climate control panel.

NOTE: disconnecting the battery will NOT clear (erase) the codes.