Pontiac Repair: transmission, 99Montana, lmap, solenoid

Question
When my car gets hot, the tranny shifts hard, RPMs jump, jerks--(no shavings in fluid & filter changed)check engine comes on.....could this be a sensor or something more serious???

Answer
Hi Polly:

More than likl;ey this transmission has a bad pressure control solenoid. It will cause the lmap to come on and hard shifts. It's pretty common on these vans. Get it fixed sooner rather than later the harsh shifts are not good and it can result in parts failure other than just the solenoid.