Hyundai Repair: Trouble Code in 2000 Sonata, transmission control module, two occassions

Question
I have been experiencing loud "thuds" in my 2000 Sonata when driving on the highway on two occassions.  After the thud, then it seems like I have to press the gas pedal pretty hard to make it go.

I had a a diagnostic test performed on it at Autozone this weekend and the error code is:  P1529; Scair solenoid circuit malfunction.

What does this mean?  How much can I expect the repair to cost?

Thanks for your time.

Answer
P1529 means nothing more than the TCM (transmission control module) has requestef the ECM (engine control module) to turn on the check engine lamp.  To find the nature of the problem, you'll need to have the codes in the TCM read.  

The reason you're having trouble accelerating is that the TCM has placed the transmission in failsafe (3rd gear only).  It'll continue in failsafe until you turn the car off and restart it.  It'll then drive normally again until the TCM redetects the problem.

The good news is that it's probably minor.  But without the TCM codes, it's impossible to make a conclusive diagnosis.