without a scantool to clear the codes, if new plugs and wires took care of the issue, it usually takes 3 full trip cycles (driving car until it is at operating temp so the ecm can run all the system checks) to turn the light off, however some codes ( i dont know what they are) by law have a 42 trip cycle count. basically the light will be off but the code stored as permanent for 42 drive cycles. emmisions standard for state inspections can have have permanent codes as long as their are no current or pending codes in the ecm