1997 ranger engine light on

tuned up truck last year and shortly after engine light came on truck ran fine then needed it smogged this year and failed because of gas cap put new one on and reset computer and at 46 miles driven light back on gas cap was off for about 10 miles last year and i think this is when light really came on but why is it passing all emissions but only failing because of gas cap which was replaced but now light back on what is a woman to do need smog to pass so i can renew registration asap PLEASE HELP:screwy: TOODARNBADK@AOL.COM

You said that the Check Engine Light (CEL) came on after tune up a year ago but you continued to drive since the vehicle seemed to be running OK. A steady CEL light on meant that you have engine or emission problem/s but it is OK to drive the vehicle BUT for you to correct the problem at the nearest opportune time. A flashing CEL on the other hand means that you have to stop the vehicle at the first safe opportune time.

When you continued to drive the vehicle with the CEL problem uncorrected, the computer module had to compensate for the problem and that's why you were able to drive with no "problem". There's a code that needs to be extracted using a device called OBDII. The code will list several possible sources of the problem. Apparently the gas cap was one possible source but it could also be others in the fuel EVAP Monitor system. I suspect that whoever did your tune-up disturbed something that caused the problem - probably the purge cannister. In retrospect, you should've gone back to the mechanic soon as you found out you had a CEL which was not there originally.

If you can, goto a reputable auto mechanic (which are hard to find) and let him/her ran a diagnotic test (cost about seventy bucks) which will pin point the sourc of the problem. i"m sure that when corrected, you'll pass the smog test with flying colors. Good luck.