P0401 / P0402
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P0401 / P0402
I have a 1996 Mazda B4000 (Ford Ranger) with the 6 cyl 4.0 engine. I was getting a code P0402 (Excessive EGR flow) with the original metal case DPFE sensor. I replaced the DPFE sensor with a new plastic case model, and now get P0401 (Insufficient EGR flow). The engine runs fine with either DPFE installed. Although possible, it is unlikely that both DPFE sensors are bad.
Thoughts?
-Dj
Thoughts?
-Dj
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Joined: Jan 2004
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From: SW Va
Welcome to FTE.
Maybe you have more than one problem.
On the orgional code, with the old DPFE sensor, maybe the problem was with a vacuum leak in the VSV diaphragm, that the computer uses to operate the EGR valve, causing the EGR to remain open & thus get too much EGR feedback.
On the replacement DPFE causing too little EGR, maybe it's bad, or it's calibration isn't up to snuff operationally, if it's an after market part.
OR, if the engine is using oil, maybe the EGR valve has some carbon build up in the DPFE feedback orifice, or interconnecting hose, thats mucking the DPFE calibration up, or causing the EGR valve to stick, or hold it open & act out????
While you were replacing the DPFE, did you pull the battery B- cable, to clear the code/s & wipe the computers memory, or ease the codes with a scanner, or scantool????
Some thoughts for pondering, let us know what you find.
Maybe you have more than one problem.
On the orgional code, with the old DPFE sensor, maybe the problem was with a vacuum leak in the VSV diaphragm, that the computer uses to operate the EGR valve, causing the EGR to remain open & thus get too much EGR feedback.
On the replacement DPFE causing too little EGR, maybe it's bad, or it's calibration isn't up to snuff operationally, if it's an after market part.
OR, if the engine is using oil, maybe the EGR valve has some carbon build up in the DPFE feedback orifice, or interconnecting hose, thats mucking the DPFE calibration up, or causing the EGR valve to stick, or hold it open & act out????
While you were replacing the DPFE, did you pull the battery B- cable, to clear the code/s & wipe the computers memory, or ease the codes with a scanner, or scantool????
Some thoughts for pondering, let us know what you find.
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Hi Pawpaw,
I cleared the codes with a scan tool. If I switch the DPFE sensors, the corresponding code follows the sensor. I suppose it is possible that the new DPFE sensor is bad, too. It should be a warranty exchange, so I can try that.
-Dj
I cleared the codes with a scan tool. If I switch the DPFE sensors, the corresponding code follows the sensor. I suppose it is possible that the new DPFE sensor is bad, too. It should be a warranty exchange, so I can try that.
-Dj
Moderator
Joined: Jan 2004
Posts: 13,851
Likes: 111
From: SW Va
If after clearing the codes, they still return & follow the DPFE sensor, then you may be right, the new sensor may be faulty.
You know the EGR valve is working, because it can provide too much EGR feedback with the old sensor, so it seems the problem might be with the signal the DPFE is sending to the computer, so both DPFE sensors are suspect.
It would seem if the VSV (Vacuum Switching Valve) were leaking vacuum to the EGR valve, causing it to remain open with the old DPFE, then it would do it with the new one & cause it give too much EGR feedback.
Just for grins, check the VSV & make sure it's diaphragm is holding vacuum & it's interconnecting vacuum lines to the EGR valve are ok, no soft, loose fitting, hard cracked, split or dryrotted rubber. The vacuum lines from the VSV to the EGR valve diaphragm need to fit snug.
You know the EGR valve is working, because it can provide too much EGR feedback with the old sensor, so it seems the problem might be with the signal the DPFE is sending to the computer, so both DPFE sensors are suspect.
It would seem if the VSV (Vacuum Switching Valve) were leaking vacuum to the EGR valve, causing it to remain open with the old DPFE, then it would do it with the new one & cause it give too much EGR feedback.
Just for grins, check the VSV & make sure it's diaphragm is holding vacuum & it's interconnecting vacuum lines to the EGR valve are ok, no soft, loose fitting, hard cracked, split or dryrotted rubber. The vacuum lines from the VSV to the EGR valve diaphragm need to fit snug.
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