1870 and 0442 Codes

My sister had her car scanned at AutoZone and received both the 1870 and 0442 codes. The 0442 code is a small emissions leak or something, most likely the gas cap. The other code, 1870, she was told has something to do with an open circuit in the traction control and most likely went on and back off when we hit a big pothole or something. However, everything I keep finding on the web, says it has something to do with transmission slippage. Does anyone have any knowledge about either of these codes and if it's a common problem that can be fixed easily? Thanks for you help.

Oh yeah, it's a 1999 Grand Prix SE with a 3.1L auto. If you need any other info, let me know, thanks.

1870?....I dont think you got the code right......

0442 = P0442 Evaporative Emission Control System Leak Detected (small leak)

maybe
1860 = TCC PWM Solenoid Circuit Electrical (GM)

As for the 0442 code I can't help him but he has the code (1870) right...i have the same problem on my 1996 grand prix se...i bought a code reader and it tells me the same thing...it keeps my check engine light on and where i live in tennessee it cause the car to fail the emissions test...how a transmission "problem" has anything to do with an emissions test is beyond me. as far as my transmission goes i don't feel any problems with it and from what i have read online about this problem...it may be caused by some soliniod (forgive my spelling of that) on the side or IN side the transmission. I have not yet ventured so far as to get under the car to see if its something i can fix. my next repairs will be dropping the fuel tank...had it replaced a few years ago but never used the car for a long long time after that and the tank leaks from the TOP when i FILL it up it over flows. Plus I have what I belive to be a bad gasket on the transmission pan. I leak fluid SOMETIMES. but it seems to stop when it gets below a certain point. I still have fluid on the stick but if i add fluid sometimes it will do ok for a while and other times it seems to be dumping the fluid on the ground AS I add it!!!

P1870....Transmission component slipping

P0442....Evaporative Emission Control System Leak Detected (small leak)

On the P1870, check the condition of the trans fluid and do a filter change if it hasn't been done.

On the P0442, check the gas cap first to be sure it's tight (always tighten to at least 3 clicks) and check the condition of the seal. If that checks out, taking it to a garage with a smoke machine is the best option, as it could be anything from a vacuum hose, vent tube running from the engine to the rear where the canister is located, to a rusty filler neck, etc...