Contour Enthusiasts Group Archives Forums General Troubleshooting Codes 402, 420, 430

My wifes mystique has been spitting out codes a lot lately. The cat codes weren't bothering me but now that the 402 (EGR Flow Excessive) code has popped up on two of the occassions with both cat codes I am starting to wonder what to look for. I looked for bad hoses to the DPFE. They all looked good and I can't find any intake leaks. Gas mileage is normal and performance is normal. The DPFE was replaced within the last 2 years. Any more suggestions.

Do the EGR suck test (aka EGR vacuum test) and plugged exhaust test.

EGR suck test (aka vacuum test).
Modified test for EGR (per Ray and Steve):
(remove the green vacuum hose from the top, be careful as it is brittle, and apply a vacuum (attached a small hose and suck on itl) to see if the car stumbles while running. This indicates a properly operating EGR.

Does it work properly?

NO: The EGR valve is defective or the EGR passages are clogged. Check (and clean, if needed) the passages behind the Throttle Body. Purchase a TB gasket, and remove the air plenum (rubber accordion tube) then remove the TB. Clean the EGR passage (small cut-out in the outer edge of the TB's mating surface) really well, install a new gasket and re-attach the TB. If the passages are clear, the EGR valve is defective. While rare, they do fail.

YES: The EGR valve works and the passages are clear. The likely fault is the DPFE sensor or its sample hoses, followed by the EVR solenoid or the PCM. May also be caused by interconnecting vacuum lines or electrical connections.

Plugged exhaust test.
For the Duratec, a good cheap way is to remove the O2 sensors, in this order (and see if the performance improves). Uninstall Bank 2 lower (radiator side) to determine if main cat is plugged, reinstall Bank 2 lower and then uninstall Bank 2 upper (radiator) to determine if Bank 2 precat is plugged, reinstall Bank 2 upper and then uninstall Bank 1 upper (hardest one, close to firewall) to determine if bank 1 precat is plugged. You don't need to mess with bank 1 lower as bank 2 lower will also be a test of that issue too (if it is an issue). Battery needs to be disconnected before uninstalling and installing O2 sensors. Good luck.

well when I had a P0402 a new PDFE sensor took care of that problem, cleaned the throttle body passages also

when you replaced the DPFE did you get the newer plastic version or the older metal one? if it was a metal one it could have failed again

It was the metal one. I guess that could be it again. Maybe I will pull the one off my SVT and see if it fixes it for awhile then get another new one if it does. I will also check the EGR just to rule it out. Thanks guys.

As for TB cleaning, this thread has some good info.
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=trouble&Number=920243&Forum=trouble&Words=p0401&Match=Entire%20Phrase&Searchpage=0&Limit=25&Old=allposts&Main=919728&Search=true#Post920243

The intake was cleaned 30,000 miles ago and it didn't look to bad last time I looked at it but good point and I will check it.

I have a question about the cats too....with the code P0420, which bank is considered bank 2? Would that be the bank closest to the firewall? I managed to pick up a used exhaust manifold pipe with the pre-cat in it from a fellow CEG'er and i just need to figure out what side it goes on.