2003 Ford Windstar 420 Code

this depends on whether or not you have an exhaust gas system module or not. but fords have a habit of eating up the exhaust gas sensor. It is in the pic that I have sent so that may be the problem as both use that. otherwise it may be the module is keeping the EGR valve open. the sensor is at the lh rear of engine compt. it is also called the dpfe sensor or differential pressure feedback EGR

thanks...We have already solved the egr problem (we replaced dpfe valve, vacuum regulator solenoid and removed intake and cleaned port for egr valve)...but now the 420 code is coming up (02 sensor seems to be working properly by scan tool and no converter rattle)...what else could be our cause?

420 is a bad converter code and with your mileage it very well cold be even if it's not rattling. there are converter clean up chemicals that you can try , don't know if they work or not however. It can also be an air leak prior to the converter but I kind of doubt it.here are possible causes in pic but it wouldn't surprise after checking this stuff that it's the converter. a pro can freeze frame to make sure it's converter.

Thanks for your help! Much Appreciated!!!