Hey guys...need to get through emissions and about to jump off bridge...

'97 4x4 with 4.6 v-8 and 5 speed...P1405 code...I tested EGR system (all OK), replaced DPFE sensor, and checked all hoses/tubes...reset computer and felt pretty confident I was going to be OK....until the Check Engine light pops back on...throws code p1405...

Coincidentally, she's been idling rough intermittently for a while and couldn't get it nailed down. A while back my 4x4 quit working so I pulled some vacuum lines to see if any had broken or any 4x4 stuff quit...blah blah blah...turns out it was the switch sensor on the transfer case...ok...fixed. Noticed rough idle some time later but didn't connect the two...until now...

Turns out I accidentally swapped the green (to EGR valve) and white (vacuum source) tubes on the EVR. I switch them back tonight... intermittent rough idle fixed!! Would this throw a p1405 code? I can't find anything to point me in the direction as an EVR problem since the code is leading me to a fault at the DPFE sensor???

Any thoughts/info. appreciated...

 

Probably not the cause of the code, but you might want to inspect the tubes from the exhaust sample tubes to the DPFE sensor....

 

Right, P1405 DPFE sensor Upstream hose off or plugged. = (Actually the lower hose)

Plugged in this context means blocked. This could either be an intentional plugging, blockage by foreign matter, kinking or melting which stops the gas flow. It is not difficult for work on the engine to knock off a sensor hose either.

BTW, this points to the Exhaust Manifold Side (EMS) side of the EGR pipe orifice. That's the longest of the two hoses and the lower one.

 

Also,- in normal operation the EGR system should be undetected by the owner. If the system fails with the EGR valve closed there will be no driveability concern. No MIL light means that the owner will remain unaware of it. Since emission testing is at idle (when the EGR does not operate) the vehicle will not fail the MOT.

However,- if the system is not gas-tight then air can be drawn into the inlet system instead of inert gas. This can weaken the mixture sufficiently to cause misfiring, and manifests itself as a noticeable misfire/hesitation at speed and light throttle, not present when accelerating. If the leak is serious enough it may manifest itself as a hunting/rolling idle, caused by an unmetered leak of air into the inlet.

 

Success!! Passed emissions this evening...full OBD test!!

Jbrew...I think I dig what you are saying...but correct me if I'm wrong;

-If the EVR is hooked up wrong, a vacuum issue will throw my mixture off causing the rough idle/misfire. It will also cause the EGR system to work improperly, but can be an undetected issue...which could explain why I didn't get any EGR codes. SO...I assume a vacuum issue at the EGR system could cause a bad mixture, the rough idle/misfire, and affect the gas flow to the DPFE, throwing a P1405 code without throwing an EGR code? So in a round about way, a P1405 can be set off by not just a bad DPFE sensor or plugged lines?

Ouch...my brain hurts...but at least she got through emissions...good grief...