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ODB Code PO406 EGR Excessive Flow
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From: colorado
ODB Code PO406 EGR Excessive Flow
I had autozone run a test on my expy. It came up with the PO406 Code. Not long ago I replaced the pressure feed back sensor which was bought from Autozone. It has worked just fine for over 8 months. Just this morning the check engine light came back on. Does anyone have any suggestions as to what might be the problem? My best guess would be that the pressure feed back sensor has know gotten stuck open hence giving me an Excessive Flow reading.... Any ideas? 
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From: DIXIE
There are two main components to the EGR system. The DPFE sensor and the EGR valve itself. The DPFE sensor is a common problem, is this what you replaced already? If so, is the new one plastic or metal? The metal ones seem to fail quickly.
If the EGR valve gets some "trash" caught in it it can stick. However, when the EGR valve actually sticks open you can tell BIG-TIME. It acts like a huge vacuum leak and the engine idles like crap, if it idles at all. I woluld say that if it seems to be running fine, thene the DPFE is sending a false signal based either on faulty info (ie. vacuum hose fell off) or the DPFE is bad.
If the DPFE is bad and sending an EGR Flow excessive code then it is keeping the EGR valve closed all the time so you wouldnt really notice any performance issues (other than a little more pinging than usual). I would say that if you are running good, look toward the sensor or the hoses feeding it rather than the EGR valve itself. I had the same code last year and replaced the DPFE to solve it.
If the EGR valve gets some "trash" caught in it it can stick. However, when the EGR valve actually sticks open you can tell BIG-TIME. It acts like a huge vacuum leak and the engine idles like crap, if it idles at all. I woluld say that if it seems to be running fine, thene the DPFE is sending a false signal based either on faulty info (ie. vacuum hose fell off) or the DPFE is bad.
If the DPFE is bad and sending an EGR Flow excessive code then it is keeping the EGR valve closed all the time so you wouldnt really notice any performance issues (other than a little more pinging than usual). I would say that if you are running good, look toward the sensor or the hoses feeding it rather than the EGR valve itself. I had the same code last year and replaced the DPFE to solve it.
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From: Long Island, NY
Could the DPFE sensor be bad and no codes thrown?
I'm asking b/c I've noticed an increase in pinging when accelerating from around 30 mph to 50mph?
I have a '98 and it has close to 125,000 on it and I'm sure it's the original?
Also, what about the O2 sensors? Any clues to determine if you need to replace them?
Thanks,
Phil
I'm asking b/c I've noticed an increase in pinging when accelerating from around 30 mph to 50mph?
I have a '98 and it has close to 125,000 on it and I'm sure it's the original?
Also, what about the O2 sensors? Any clues to determine if you need to replace them?
Thanks,
Phil
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From: colorado
obd Code PO406
The new sensor that I put in is a metal sensor. I have heard of problems with the metal sensor vs.'s the plastic sensor. The truck seems to be running just fine and I have not really noticed any pinging in the motor. The only place that sells the plastic sensors is the dealer no? thanks for your input....
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From: DIXIE
The new sensor that I put in is a metal sensor. I have heard of problems with the metal sensor vs.'s the plastic sensor. The truck seems to be running just fine and I have not really noticed any pinging in the motor. The only place that sells the plastic sensors is the dealer no? thanks for your input....
If you want to see if the EGR valve is sticking, put a vacuum pump on it and see if it the motor dies when you "pump it up" at idle. If it does, look for loose or broken connections at or around the EGR valve and DPFE sensor. If you don't see any, I would say that the DPFE is a fair bet for being the culprit.
Could the DPFE sensor be bad and no codes thrown?
I'm asking b/c I've noticed an increase in pinging when accelerating from around 30 mph to 50mph?
I'm asking b/c I've noticed an increase in pinging when accelerating from around 30 mph to 50mph?
Last edited by jbabbler; Oct 20, 2004 at 02:35 PM.
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From: colorado
OBD Code Po406
I will try the vacum gauge and let you know what I came up with. Thanks for the input on where I can buy a plastic DPFE sensor. I will post later and let you know what I came up with. 
Thanks Ajdawg
Thanks Ajdawg
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From: Long Island, NY
Originally Posted by jbabbler
Anything is possible. The DPFE may be causing your truck to ping but before I assumed that I would look elsewhere. First thing I would do is to clean the MAS (Mass Airflow Sensor) very very well. It measures the airflow coming into the engine and if dirty can cause significant pinging and performance issues including excessive fuel consumption. I would also change the fuel filter (If you haven't recently) and the air filter. Pinging is usually caused by incorrect timing and/or fuel delivery. "Pinging" is actually pre-detonation of the gas/air mixture. Low Octane Gas can also cause "pinging". The higher the octane reading the slower the gas is to detonate. If you got a batch of bad fuel it could cause the same symptoms.
Thanks for the response, I just changed the air filter, and cleaned the MAS this past weekend. I've been running Mobil 87 octane since I got it b/c gas around here is 2.20 for 87 octane. Just wondering b/c I also took off the throttle body and cleaned that out as well.
Thanks again. - Phil
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