You should be able to go to a local autozone and they'll pull the codes off for free. Once you have the code, you can search this forum for it - you'll prolly find someone has already had that problem and you'll know what to replace.
MEV Rocket - JRSC BBK powered. 1350lbs / 190whp
E46 M3 vert, bone stock daily driver
'99 F350 7.3 diesel 4x4 Dually - chip, 4" exhaust, intake mod, stg1 injectors.
In a past life: '02 ZX3 - Built motor, GT28RS, LSD, 4.06 gear, Spec stg3 clutch