Scan Codes Diagnosing, 3.8 Taurus Wagon and Check Engine Light

My Check Engine light came on while I was driving on a long trip. I read up on this and it seem to indicate that the most likely reason is something wrong with the pollution stuff. And that the best way to sort this out was
get the scan codes and investigate.
I have jumpered the wires on the connector block and got the Scan codes out of my car. The best I can figure out they are as follows. 0 327 (O,C,R) EGR Valve Pressure Transducer/Position Sensor circuit below minimum voltage C 326 (C,R) EGR circuit voltage lower than expected C 337 (O,C,R) EGR Valve Pressure Transducer/Position Sensor circuit above maximum voltage R 536 (O,C,R) Brake On/Off Switch Circuit failure R 521 (R) Wheel not turned during test or PSP problem - PSP R 327 (O,C,R) EGR Valve Pressure Transducer/Position Sensor circuit below minimum voltage
Again in my reading it seemed that the most common thing that goes is the EGR Valve and with all of the mention of the EGR in the error message I decided to replace it. I have done that but the light still comes on. Should the light automatically go off if the problem is fixed or can anyone see from the scan codes above if I was wrong. I note that it appears that the pertinent errors all seem to be related to voltage. So perhaps I was too quick to replace EGR since there are no electrical components in the EGR. There is however a small pipe running from the EGR to a device that has some sort of electrical 3 wired device on it that must measure pressure of some sort.
Can anyone give me some advice on how to proceed with this.
Regards Steve 7Willie
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I never worked on a Taurus, but here are few general hints: 1. I am guessing that your vehicle is from the early 90's. Alway post the year and mileage of your vehicle, if you want advice. 2. Most KOER tests require you to tap the brake, turn the steering wheel, and push the OD button on the transmission (if yours is an automatic with overdrive). Seems that your codes 536 and 521 showed up simply because you did not do those things. 3. Throwing parts at a problem that you don't understand rarely helps. The trouble codes give you a general direction, but almost never pinpoint the defective part. There simply is no substitute to reading a good manual, understanding how the system that you are attempting to repair works, and equipping yourself with at least the basic tools for the job (a DVM and a hand-held vacuum pump if you are working on an EGR).
As far as your EGR problem goes, the EGR valve is a mechanical, vacuum-operated device, which controls the flow of a small portion of exhaust gas into the intake manifold when conditions are right. The computer manipulates the opening of the valve by applying vacuum through a solenoid (or regulator) in response to the EGR flow, which it measures through some sort of a pressure sensor. The whole system is relatively simple, but as you can see, has several components, all of which can fail, clog, leak, or disconnect. Ford used at least 3 different types of EGR systems over the years, and one of them may have an electronic control module in addition to what I described. I believe that if you post the model year, someone on this group will know what exactly you have, but otherwise it's hard to give any specific advice. If I may risk a guess, the pressure sensor (either a PFE or a DPFE) is the most fragile part, because it has electronic parts subjected to the constant barrage of hot exhaust. I would, however, advise you once again to do methodical troubleshooting, and not follow my (or anybody else's) guess.
Good luck,
IK
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Thanks for your tips. Sorry about the year. In 99 percent of the time I usually do post the year of my car, it seems in this case I forgot after typing my essay. The year is 1994. It has about 200,000 km on it. For the most part the car runs fine. (After replacing the transmission and seals on the heads. And it having no camber adjustment on the rear.) I have a manual, which is how I figured out how to get the codes and what they all mean. As far as the codes 536 and 521. I did turn the wheel to the left and to the right and put my foot on the brake when I thought I was suppose to. Obviously it didnt like when I did it or didnt register it. I only provided the full list of scan codes for completness. I asume that those codes are being reported because I didn't do it right at the time. I did do it several times but it still gave me the same "error code" I'm not really worrying about them at this point because I dont think they have anything to do with my check engine light, which is my current battle. As I said I have a manual. Unfortunetely it doesnt always tell you how to diagnose problems just how to replace things. It tells you how to replace a lot of the important components, which is simple as anything but far be it for them to say put a volt meter here or a vacume gage there and see what the voltage/pressure is etc. They just like to waste paper so it looks like they are thick with information. Unfortunetely a thick book is no more good information that a pile of garbage is a mountain. But I digress.
Does this informaion help narrow down the culpret ?
Regards steve 7willie
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Workshop manuals deal with assembly/disassembly. If you don't already have it, get the Ford 'Emissions/Engine Electronics' (or whatever it's called for your year). It covers every car and truck for the model year. Helm (doing on line business as helminc.com) sells it for a rather hefty price, either in binder or CD form. Check Ebay as well. Even this book won't tell you how things work; it will just provide the diagnostic procedures. A decent text, which will explain things is Charles Probst's 'Ford Fuel Injection & Electronic Control'.
IK
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Since you didn't indicate what year, I can only guess, but the codes indicate the DPFE/PFE sensor, which measures EGR flow via exhaust back pressure. the 521 code is obvious.
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Sorry the year is 1994 with about 200,000km on it. The DPFE/PFE is this the part that is connected to the EGR via a small tube (about 1 inch) with 3 wires connected to it.
Regards Steve 7willie
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Yes, the codes indicate this part is failing. Common when the cool nights arrive, moisture causes the codes.
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If the light keeps coming on, it's not fixed. You should have checked for vacuum to the EGR solenoid, a complete vacuum line from the solenoid to the valve. How is the EGR sense hose? How is the sensor? A code for EGR or any part for that matter does not mean to replace the part.

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Yes your right on checking for vacum. I didnt. But I figured even if there was vacum it didnt really tell me if the EGR was working or not. I did look at all the hoses and tryed to examine condition which all seem to be good. I dont have a vacum gage. The reality is that the manual I have doesnt say what any of the pressures should be so even if I had one It would not have helped me. I have learned that sometimes buying the tools is worth it but if you don't know how to use them properly then its useless. Any other advice would be appreciated.
Regards steve 7willie

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