Code P0401 - possible bad DPFE sensor
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Junior User
Joined: Jun 2004
Posts: 66
Likes: 1
From: Big Rapids, MI
Code P0401 - possible bad DPFE sensor
Hello - have had a CEL on our '96 Explorer for quite some time now. The only code is P0401 - EGR Insufficient Flow Detected.
Based on other previous posts in this forum, and info found elsewhere on the internet, it sounds like Explorers of this year that have a P0401 code typically have a bad DPFE sensor.
I have the Haynes repair manual for the vehicle. It details some testing procedures for the DPFE sensor. The reference voltage is checking out okay - it's supposed to be between 4.0 and 6.0 volts and I'm getting just over 4.0. The signal voltage is what I'm wondering about though. I don't have the manual in front of me so I can't quote it word for word, but it basically says to backprobe the SIG and GND terminals and check the voltage with the engine on first at cold temperature, then at warm operating temperature. There is no GND terminal on the sensor, so I'm grounding the negative lead on my multimeter to the alternator, and that seems to be working fine. I can't imagine how that would affect my test results, but I'm not very knowledgable about automotive electronics so I figured I'd mention that just in case. Anyway, the voltage I'm getting on the SIG terminal is supposed to be roughly between 0.35 and 0.8 volts (I have the aluminum sensor, not the black plastic one) when the engine is on and cold...but I'm getting just a tad under 4 volts.
Assuming that I'm running the voltage test properly, my question then is: does this mean that my DPFE sensor is bad and needs to be replaced? or does it mean that some other component that is feeding into the DPFE sensor is bad?
2nd part to my question: anyone familiar with these DPFE sensors...is there any reason to purchase a replacement sensor directly from the Ford dealer, as opposed to purchasing one from AutoZone or some other similar store? The Ford dealer quoted me a price of $85 for a new sensor. AutoZone has one manufactured by Wells (part number SU282) for $53.99.
Thanks in advance for any help you can give me!
Based on other previous posts in this forum, and info found elsewhere on the internet, it sounds like Explorers of this year that have a P0401 code typically have a bad DPFE sensor.
I have the Haynes repair manual for the vehicle. It details some testing procedures for the DPFE sensor. The reference voltage is checking out okay - it's supposed to be between 4.0 and 6.0 volts and I'm getting just over 4.0. The signal voltage is what I'm wondering about though. I don't have the manual in front of me so I can't quote it word for word, but it basically says to backprobe the SIG and GND terminals and check the voltage with the engine on first at cold temperature, then at warm operating temperature. There is no GND terminal on the sensor, so I'm grounding the negative lead on my multimeter to the alternator, and that seems to be working fine. I can't imagine how that would affect my test results, but I'm not very knowledgable about automotive electronics so I figured I'd mention that just in case. Anyway, the voltage I'm getting on the SIG terminal is supposed to be roughly between 0.35 and 0.8 volts (I have the aluminum sensor, not the black plastic one) when the engine is on and cold...but I'm getting just a tad under 4 volts.
Assuming that I'm running the voltage test properly, my question then is: does this mean that my DPFE sensor is bad and needs to be replaced? or does it mean that some other component that is feeding into the DPFE sensor is bad?
2nd part to my question: anyone familiar with these DPFE sensors...is there any reason to purchase a replacement sensor directly from the Ford dealer, as opposed to purchasing one from AutoZone or some other similar store? The Ford dealer quoted me a price of $85 for a new sensor. AutoZone has one manufactured by Wells (part number SU282) for $53.99.
Thanks in advance for any help you can give me!
Freshman User
Joined: Jan 2005
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I thought the same as you and suspected the DPFE but had a shop test the egr valve and it tested bad. I replaced the egr valve and had no more problems.
Chances are that the wells parts are ok. If it was $1.95, I'd be suspicious. Also, it's not like it's a 'brand new for aftermarket inventory' part.
peace and good luck,
da Celt
Chances are that the wells parts are ok. If it was $1.95, I'd be suspicious. Also, it's not like it's a 'brand new for aftermarket inventory' part.
peace and good luck,
da Celt
Thread Starter
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Junior User
Joined: Jun 2004
Posts: 66
Likes: 1
From: Big Rapids, MI
I didn't really want to spring $54-$85 for a new sensor, since I wasn't 100% sure that's what the problem was. I searched on eBay and found someone selling a DPFE sensor from a 1996 Mercury Mystique. The part number was exactly the same as mine. The car they pulled it from only had 65,000 miles, and the CEL light wasn't on...so I figured I'd give it a shot. It cost me $21 including shipping.
Disconnected the negative terminal on the battery, pulled the old DPFE sensor off, popped in the new (used) one, hooked the battery back up (I had it unhooked for at least 15 minutes, as I read somewhere it had to be disconnected for that long to clear the CEL codes), and everything has been fine since. The CEL light went off and hasn't come back on. That was one week ago, so I think everything is good now.
Disconnected the negative terminal on the battery, pulled the old DPFE sensor off, popped in the new (used) one, hooked the battery back up (I had it unhooked for at least 15 minutes, as I read somewhere it had to be disconnected for that long to clear the CEL codes), and everything has been fine since. The CEL light went off and hasn't come back on. That was one week ago, so I think everything is good now.
