Hi all,

Cleaned battery corrosion and reconnected the battery and am now getting a P0402 code. The timing made me wonder if I knocked something loose, but I know the code relates to the EGR pressure sensor or valve or perhaps a vaccum leak..

It's also worth noting that the front driver-side catalytic coverter is a little noisy but, as I understand it, that would usually throw another code. Replaced the cam synchro recently but I don't think that's related either.

In any event, I'm wondering where to start. Seems like the best starting point would be the pressure sensor (I've read it's best to get the Standard or Motorcraft brands) but also wondering if it makes sense to clean the existing EGR valve first?

The sensor's not overly expensive but I don't want to just start replacing parts if there's something obvious I can look for or do to troubleshoot first. I guess I'd rather swap out the sensor before trying to diagnose a vaccum leak as I've never done that before, though.

Any direction would be appreciated so I can get started! There may be a slight loss of acceleration (hard to tell) but the truck's not stuttering or stalling at all...and I hope driving it like this doesn't jeopardize the engine at all. Hard to say as I'm not sure what's causing the code!

 

Always good to look up codes on a full list, so you can see what its not

P0400 Exhaust Gas Recirculation Flow Malfunction
P0401 Exhaust Gas Recirculation Flow Insufficient Detected
P0402 Exhaust Gas Recirculation Flow Excessive Detected
P0403 Exhaust Gas Recirculation Circuit Malfunction
P0404 Exhaust Gas Recirculation Circuit Range/Performance

Not a circuit/electrical issue

"flow" thru the EGR valve is determined by 2 hoses connected to EGR pipe
Other ends of the 2 hoses are connected to the DPFE(pressure feedback) sensor
DPFE "sees" the pressure difference between the 2 hoses, if the pressure on the hose closer to the EGR valve is lower then EGR valve has "flow"
If pressure is equal then no flow
If pressure difference is large then "Excessive" flow

So P0402 means DPFE "sees" a large pressure difference, if EGR valve was stuck open engine would run VERY poorly, and you don't mention that, so not an EGR valve issue

So first check the 2 hoses, they can get water inside or crack or be pulled off at either end

These hoses have Exhaust inside, exhaust has water vapor, so water can condense in the hoses and even the DPFE sensor which causes issues

 

Hi Ron,

Thanks for the knowledge!

The hoses look good and aren't cracked or pulled off at either end. I can say that the sheathing around the EGR pipes (just below where the hoses connect to them) is a little ripped around the pipes. Not sure why or if that matters.

Do you think it makes sense to just replace the sensor at this point? It's metal and I read that they are prone to fail and best replaced with plastic ones - either Motorcraft or Standard. Or maybe it would be best to replace the hoses and the sensor?

 

You can pull off 1 hose at a time from DPFE and blow thru it to make sure its clear, its open at exhaust end or should be, lol

Yes, DPFE sensors do fail, try unplugging its 3 wire connector and plugging it back in, that cleans the contacts
If a sensor fails you usually get a "Circuit" code

Replacing sensors are a last resort
90% of DIY sensor replacement wasn't needed
60% of pro-mechanic sensor replacement wasn't needed, but that's usually to pad the bill, lol

But you are correct DPFE sensors do have a poor track record, because of the water, which is why plastic housings are often better, less condensation internally

 

Reset the 3-wire connector but the check engine light is still on. It was pretty dusty.

Is there a trick to disconnecting those hoses? Maybe I wasn't angry enough but dang they're on there!

 

Yes, they will be hard and tight, heat from exhaust, two different sizes so you don't mix them up

 

I reset the battery for a couple of minutes and the code never came back. I sure appreciate your help, Ron!

I'll keep my fingers crossed for now.