check engine - ETS off indicators

I have a '97 Cavalier 2.2 auto trans. While driving, had to hit brakes - HARD, but no wheel lock-up. Afterwards, engine RPM seemed to float from idle to 1200 RPM. Car shifted hard twice, then smoothed out. Parked car for 20 minutes, turning off engine, then started to drive, and noticed that "check engine" and "ETS off" lamps are illuminated, but are not flashing. Car now runs great, just like before the hard brake, except for the fault lamps. Local dealer thinks disconnecting battery will clear fault. One mechanic thinks perhaps fuel was in evaporative cannister and was injested by motor during the hard brake. Any ideas?
Thanks,
Ray

Umm..... have the codes read and computer cleared then come back and tell us what they say.