Error Code P0402 w overdrive transmission shifting problem

[Ironhorse-nd]

95 ranger xlt with the 3.0 v6 2wd.

I have an error code that triggered the CEL. I scanned it and had the PO402 "Exhaust Gas recirculation flow excessive Detected" warning pop up. After researching the code it sounds like that could be my EGR valve or the DPFE sensor. From searching the forums, it sounds like its most likely my DPFE sensor is much more common that the actual EGR itself.

I'm wondering if this is related to a shifting issue in my OD tranny? The transmission seems to work fine except when it goes into overdrive. Once it gets there, it seems like it wants to downshift but doesn't, and shudders.

The transmission works fine otherwise other than taking a second or two to engage in drive and it shifts a little hard into reverse, but other than those issues it seems to work fine. No slipping. No flashing OD light or anything like that. If I drive it without the overdrive on I have no issues with any other gear. It kind of feels like the torque converter locks up and then releases. That's just an uneducated guess. Maybe the tranny is shot. I don't know, but it seems to work fine other than what I mentioned above.

I read some forum postings here about what the transmission problem might be and saw somewhere that the O2 sensor could be the culprit and be affecting the torque converter lock up.

I guess I wasn't sure exactly where to post everything here since I'm a noob. I posted in both the 3.0 engine forum and the transmission form since it is actually a problem with both items but I apologize in advance if this is considered a double post.

Thanks in advance for any suggestions/help you may give!

D

 

[Rearanger]

If the EGR is sticking/stuck open then that is a vacuum leak that will affect performance. I'd trace the EGR problem first then see if the other problem still exists.

 

[TimR]

Fords are also finicky about fluid changes, have the tranny flushed, with a machine that replaces ALL of the fluid, not just what is in the pan.

 

[Ironhorse-nd]

Thanks for the suggestions guys. Do you think by tracing the egr problem I should start with the egr or the dpfe?

Most threads I've read suggest the dpfe is more likely the starting point for parts replacement. I would imagine start with chiecking the hoses for any wear or leaks and then begin replacing either ghe egr or dpfe. Is that correct?

The fluid was changed roughly 20k ago, but still wouldn't be a bad preventative measure.

 

[4.0B2]

in my history of dealing w/ fords and this problem... its usually a vacuum leak in the egr circuit.

 

[Ironhorse-nd]

Thanks much for your reply. And by leak in the egr circuit, do you mean the controller (dpfe), the egr valve, vacuum lines or all of the above?

Seems like most of the old threads I've found suggest the dpfe is usually the problem in 99% of these cases, and that the egr valve itself is rarely the problem.

Thanks again,

D

 

[McCormack]

Usually the DPFE sensor itself goes bad.