Mileliminators trick the PCM by sending a signal to show that the pre-cats are working. If your pre-cats are bad or if you have headers, these will eliminate the P0420 Bank 1 and P0430 Bank 2 codes. Note that other codes not related to the pre-cats will still be sent to the PCM and light up the CEL.

"Always do the cheap and easy ones first." 1996 V6 ATX 96K miles