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Ron
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 26714
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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1995 Ford Explorer: check engine light..Egr valve..exhaust..Vacuum

Customer Question

I have a 1995 Ford Explorer with a 4.0 liter engine. The check engine light comes on shortly after warmup and stays on, setting a code 327, Egr valve position or exhaust pressure transducer circuit below minimum voltage. The EGR valve looks alright as I can put Vacuum to it and it holds and I can here it go up and down when I release vacuum. I was then told by a Local Ford garage that he could almost guarantee that it was the PFE switch. Though I got this one out of a salvage yard it looked like new. I replaced it and still have the same problem. I also replaced the other sensor that provides the vacuum directly to the EGR and also no luck. Any help you can give on this would be a great help as I am not sure what to try anymore. Oh I also checked for any obstructions in the exhaust tubes and found nothing. HELP!! (Egr feedback says 0.0 volts)
Submitted: 5 years ago.
Category: Ford
Expert:  Ron replied 5 years ago.

HiCustomer

 

Thank you for asking your question on JustAnswer.

There are sever things that can set this codes so lets start here.

 

 

incorrect installation of the Differential Pressure Feedback EGR (DPFE) sensor sense tubes from the Exhaust Gas Recirculation (EGR) delivery pipe
Defective Differential Pressure Feedback EGR (DPFE) sensor

 

Monitor the output of the Differential Pressure Feedback EGR (DPFE) sensor signal circuit, Brown/Green, with a voltmeter, when opening the Exhaust Gas Recirculation (EGR) valve with the engine running. Voltage should start at 0.4 volts to 0.6 volts, when equipped with the oval aluminum sensor and 0.9 volts to 1.1 volts with the small square replacement sensor and smoothly increase as vacuum is applied to the EGR valve.

 

The Differential Pressure Feedback EGR (DPFE) sensor voltage should show 0.4-1.2 volts Key On, Engine Off (KOEO) and at idle, when the Exhaust Gas Recirculation (EGR) valve is opened with the engine running, the voltage should increase. If the voltage decreases, the sensors "sense" tubes are hooked up backwards. Looking at the Differential Pressure Feedback EGR (DPFE) sensor, the reference (REF) ports line should be connected to the delivery tubes pipe, which is closer to the Exhaust Gas Recirculation (EGR) valve than the exhaust manifold, and the HI port should be connected to the pipe which is closer to the exhaust manifold than the Exhaust Gas Recirculation (EGR) valve. The code will set when the sensor output voltage drops to 0.2 volts or less.

 

 

Customer: replied 5 years ago.
The tubes are correcly installed as the are of slightly differant sizes to corespond to the correct port. I am reading 0.0 volts from my EZ-scan tool whther at idle or increasing throttle. Do I still need to be reading this at the sensor? Says EGR feedback 0 volts
Expert:  Ron replied 5 years ago.
The Differential Pressure Feedback EGR (DPFE) sensor voltage should show 0.4-1.2 volts Key On, Engine Off (KOEO) and at idle, when the Exhaust Gas Recirculation (EGR) valve is opened with the engine running, the voltage should increase.
Customer: replied 5 years ago.
So I do not have any ,where is the problem If I already replaced the sensor and the tubes I hooked correctly?
Expert:  Ron replied 5 years ago.
Then I would say you have an issue with eaither your PCM (computer) or the wiring to or from it to the DPFE.
Customer: replied 5 years ago.

If I remove the plug connector, turn the key on, should I be reading any voltage at the connector, going to the brown/ green wire to ground? I am not reading any voltage at the connector doing this. Must engine be warmed up first or should I be seeing voltage there all the time.

Expert:  Ron replied 5 years ago.
You should see reference voltage as long as the key is on.It dosnt matter if the engine is warm or cold.
Customer: replied 5 years ago.
So if I am not seeing any voltage at the connector with the connector disconnected I can assume the problem is before the connector, probably wire coming from computer or the computer itself, and if you were to guess which would be the more likely cause?
Expert:  Ron replied 5 years ago.
I would start at the connector and work my way back.Make sure there is 5v on the Brown/White (BN/W) wire, the Grey/Red (GY/R) wire is ground and must read 0.1v or less at all times. The signal wire is the Brown/Green (BN/GN) and should read as listed above.
Customer: replied 5 years ago.

Can I just use the battery ground which is close, and probe these wires at the connector and see what I have because I am not getting any voltage at any of these wires to ground or should I be doing this differently. It is unlikely that I would not see any voltage on any of the wires if it was a wire problem. am I right here or not

Expert:  Ron replied 5 years ago.
Yes your right and yes you can use the battery ground. You should see at least the reference voltage (5volts) on the brown wire. Be sure to back probe the connector .
Customer: replied 5 years ago.
I guess I am not sure what you mean by back probing the connector. I have the connector off and am testing it from the front, I am not seeing a good way to probe it from the back
Expert:  Ron replied 5 years ago.
From the back you may need a small straight pin to penetrate the wire.
Customer: replied 5 years ago.
hang tight I will give it a try
Expert:  Ron replied 5 years ago.
Ok
Expert:  Ron replied 5 years ago.

Enclosed is the scamatic for the PFE and you should be able to check Vref voltage on the same wire at the TP sensor.

 

graphic

Customer: replied 5 years ago.
These are my readings, Gray/ Red - .07 volts, BR/ green- .02 volts, Br/ white- .01 volts
Expert:  Ron replied 5 years ago.
Check and see if you have the 5volts on the brown/white at the throttle position sensor as its the same circuit.
Customer: replied 5 years ago.
ok
Expert:  Ron replied 5 years ago.
Look at the scamatic I sent you.
Customer: replied 5 years ago.
Yes I do have 5 volts at the TPS
Expert:  Ron replied 5 years ago.
Ok that means the PCM is ok and sending the VREF voltage, your open somewhere from the PCM to the PFE, Its just a matter of tracing it down.
Customer: replied 5 years ago.
Easier said than done but good job, it helps to have schematic to go off of. Just out of curiousity if I ran A temporary jumper from the tps ref. wire to the pfe and see if it all works would that do it?
Expert:  Ron replied 5 years ago.
Yes providing the VREF at the PFE isnt shorted to ground.
Customer: replied 5 years ago.
Gotcha, Great Job of troubleshooting and hopefully that is the only wire that is bad in the circuit.
Expert:  Ron replied 5 years ago.

Your very welcome. Its likely open in the harness someplace and yes some time can be a bear to find.

 

Customer: replied 5 years ago.
Do you know where the wire would first go back to, you said harness but am not sure where you would be talking about. The tps and and pfe must join somewhere would this be at the harness?
Expert:  Ron replied 5 years ago.
There is a major splice S128 but it in the harness between the PCM and the engine compartment. I dont have a excate location. You could likely get away with overlaying a new wire.
Customer: replied 5 years ago.
by overlaying a new wire would that mean coming from the harness connection or somewhere else
Expert:  Ron replied 5 years ago.
Yes it would mean coming from the harness where you know you have the 5 volts VREF signel and running it to you PFE connector.
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 26714
Experience: 23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
Ron and 8 other Ford Specialists are ready to help you
Customer: replied 5 years ago.
Ok, again many thanks for your patience on this matter and hopefully I can follow this back until I find good wire.
Customer: replied 5 years ago.
Thanks again, already found short, you know your Fords, excellent job troubleshooting
Expert:  Ron replied 5 years ago.
Thank you.

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