I picked up a code reader from Wally world (wal-mart) the other day. Hooked it up and it retrieved a few codes, found out that the egr valve wasn't closing properly, replaced it. Ran the tester again, code went away, then tested the truck again and the reader picks up EVP voltage was low, changed the evp sensor. Ran the tester again and now it has EGR pressure feeback fault. I have no clue what could be causing this. Plus, my truck is idling high now that I have replaced the egr valve. What would cause this and the EGR pressure feedback fault? Any suggestions...

 

The pressure feedback fault means that the DPFE sensor (or its wiring) is either bad or the EGR system has too much or too little flow. The DPFE sensor is a little silver box about 3/4" thick x 1.5" high by 3.5" long. It has a wiring harness connector and what look like two big vacuum lines hooked to it. It is located at the right rear of the engine towards the top. To test it you need to have a volt meter. With the key on and the engine not running you should have 1 wire in the connector with 5 volts, one with 1V or less, and one that is a ground. Connect the volt meter up between the wire with 1V and the ground and start the engine. The connector must be plugged in when you do this. Apply engine vacuum to the EGR valve to open it. The 1V signal should increase to between 4 and 5 volts. If the engine starts running like crap when you put vacuum to the EGR valve, but the signal doesn't increase very much or at all the DPFE is bad. If the engine doesn't start running bad there is no EGR flow for some reason.

If the high idle started after replacing the EGR valve you probably have a vacuum leak, or the truck learned to compesate for a stuck open EGR vavle before and hasn't relearned how to run with the new one yet.

 

Thanks for responding, I will test the DPFE sensor tomorrow.

 

also, what does DPFE stand for? I am having a heck of a time trying to find it. You or anybody wouldn't happen to have a picture of where it is located? Thanks again for any help.

 

It stands for Dynamic Pressure Feedback-EGR. Basically, it measures pressure across a metered orifice in the EGR tube so the PCM can calculate actual EGR flow. If you follow the EGR tube up from the exhaust manifold you should come across to smaller tubes that branch off from it, one is about 1/4" diameter the other slightly larger. Follow those tubes and they connect to the DPFE sensor via the hoses I mentioned before.

 

What is the cost of a dpfe sensor?

 

Thanks agian for responding Silver. I will look again tomorrow.

dtaylor...I'm not sure on the price of the sensor, but, I will call around tomorrow...

 

Is DPFE attached to the valve cover?

 

The DPFE sensor from Standard lists for $83, but you can probably get it for about $60.

I don't think it is hooked to the valve cover, but it might be. My service database doesn't even list a location for one, but I know they were used on the 96's.

 

My truck is an '87...and I found out what that thing is connected to the valve cover, it's an egr solenoid. I was reading in the chilton book, and it talks about Pressure feedback Electronic transducer, but it doesn't say where it is located on the truck. The hunt continues....

 

I thought it was a 96 because of the 96 in you user name. Oops. I can look up a location for that transducer, but we are having software problems right now. Maybe tomorrow I can check on it.

 

lol....it's all good. That would be great if you could do that for me...Also, my friend talked to his dad, and he said that this studder could be caused by a bad O2 sensor, I don't know, I'm going to change it anyway, because it is probably the original. Tomorrow is my graduation day from college, so, I'll be busy with that...thanks for all your help silver.

 

I can't find anything about an electronic transducer, but there is a pressure feedback transducer that is in some EGR valves. Basically, it is a check valve that prevents the EGR valve from opening when there is no exhaust back pressure present. This valve is located inside the EGR valve. Are you sure you got the right valve? Is the truck carb or EFI? It shows both in 87.

 

Yeah, I'm pretty sure that I got the right EGR valve...My truck is an EFI.

Would the egr solenoid cause the problem, because the green vacuum hose connected to the egr, is connected to the solenoid.

 

Changed the O2 sesnor today, and still no help...I'm really struggling with this one...Although I did get rid of the EGR pressure feeback fault. Now the reader is spitting up the code 33c egr fault/ not closing properly, but it is a brand new egr valve....so I'm pretty much stumped...any help would be great....