Originally posted by Nate Payeur:
They have a TSB on the PCM reflash:

TSB 04-15-16

08/09/04
MALFUNCTION INDICATOR LAMP (MIL)
ILLUMINATED WITH DIAGNOSTIC TROUBLE CODE(S)
P0420 AND/OR P0430

FORD:
1997-1998 Contour

MERCURY:
1997-1998 Mystique
1999 Cougar

ISSUE

Some 1997-1998 Contour/Mystique and 1999 Cougar vehicles ...



I would never have this TSB done. Re-flashing the PCM to deal with the P0420/P0430 code is not going to improve the pre-cat efficiency at all. It simply lowers the threshold so that a low efficient pre-cat that was to fail the pre-cat efficiency self test before the re-flashing passes the test after the re-flashing. I believe this TSB is much more effective in kicking people having P0420/P0430 out of 13yr/130KKm waranty, by postponing the re-appearance of the same codes, than it is in solving the real problem. And the most lovely part here is that the bill is on customers.

I had the same P0420 code with my 97 Tour a few months ago at 135K km out of waranty so I'm on my own, no other codes but this solo P0420. I cleared it up and turned off the CEL and it didn't come back until 3 months after. I passed the emission test with flying colors a few weeks before the code came back. So I knew the not-as-effective pre-cats are not a too big deal in the emission control as long as the main cat works well. I built an MIL Eliminator and installed it on the bank 1 down-stream O2 sensor to fool the PCM, and the code hasn't come back so far.

1997 Contour Sport Duratec MTX 2000 Olds Intrigue GLS Sterling Edition