Hi Y'all,
I've got a 1999 Explorer with 68k miles, and the small hose going to the DPFE sensor recently developed a hole/crack right where it connects to the sensor. The exhaust escaping through the hole melted the sensor and plug, and threw a CEL. Since I didn't notice the melted carnage, I got the code read at Advance and it came out as a P1401. So then I replaced the DPFE and plug, and disconnected the battery to turn off the CEL. Great. Then I took the vehicle to the store, and still no problems. On the way back, though , the CEL came back on, and this time it was P0401-- EGR flow insufficient. I've heard that the P0401 takes 2 drive cycles to turn on the CEL, which fits with what happened the first time. However, I disconnected the battery again (for a much longer period) and it took 3 drive cycles to come back on.

Anybody know what's going on here? I have three hypotheses:
1) Maybe I messed up the DPFE installation. But if I somehow messed up the DPFE installation, wouldn't it show up as the P1401 code again?

2) Perhaps the DPFE failure caused a failure of some sort with the EGR.

3) I've heard that the PCM has to "relearn" how to deal with the data sent by the new DPFE, and that it could take several drive cycles for this to happen. This would be great, but I'm trying to sell the thing and need to get the CEL off NOW!

Thanks in advance for any advice you can give!

 

The DPFE passages in the EGR tube may be clogged, the hoses may be clogged connecting to the DPFE... or the EGR system may really have a problem (which is what the DPFE system is supposed to detect)... clean out your EGR system / valve / pipes / hoses and the DPFE hoses / passages ... and then clear the codes, see if it comes back.

 

Thanks Explorer02 for the reply. I should have said in my original post that I also replaced the DPFE hoses-- so it's not those. I think I will clean out the EGR system though, and maybe test the EGR by applying suction while idling.

What's strange is that when I first replaced the DPFE, it took 2 drive cycles (as expected) for the P0401 code to show up a CEL, then I cleared the CEL and it took 3 drive cycles for the CEL to come on, then I cleared again and it took 5 cycles to get a CEL. Maybe the PCM really is adjusting to the new sensor?