i have a 2000 monte carlo ss and i got these codes when i did a obd test.

"po412 Air switching valve a problem"
"p1811 Maximum adapt and long shift"

any ideas what these codes mean and how i can fix the problem? thanks for the help.

 

P0412 indicates an issue with your AIR pump/solenoid. I believe the solenoid is under the coils, but I'm not 100% on that.

The P1811 means the transmission is struggling. One of two things is your issue - a solenoid in the transmission (pressure control solenoid most likely) has gone bad, or the transmission is on it's last leg...

 

transmission actually feels fine it doesn't shift hard at all so im hoping its just a solenoid...unless it doesnt matter if it feels like its not shifting hard. every shift is still very smooth. also the engine check light comes on once in a long while, then disappears when i dont drive the car for a day if that info is any help.

 

car doesn't shift into overdrive on the freeway. Does that info help narrow down the possible problem in the transmission?

 

Could be a solenoid or the torque converter going bad