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Old 06-21-2012, 10:03 PM
jfeazell jfeazell is offline
Learning to use the forums
Join Date: Jun 2012
Posts: 6
Default Re: EGR Flow Insufficient (PO401)

FWIW... I have heard that the purpose of the EGR is to lower the temperature of the combustion chamber in order to reduce emissions... and that when it's not working, the higher temperature of the exhaust gas "can" hurt your catalytic converter... Of course, that was told to me by someone at a shop with a vested interest in me having them work on my truck, so who knows.

FYI... On the DPFE sensor location... There are three parts (that I know of) to the EGR system. The EGR valve itself is up on top of the monifold... Looks like the saucer section of the Starship Enterprise w/ a vacuum line (green) going into the center of it. It is opened by the EGR solenoid, which is located on the left side of the motor (as you're facting the truck), just behind and below the coil packs. The solenoid has an electronic connector that tells it when to open. There is a little double boot on it with a red vacuum line that comes down from the manifold, and the green vacuum line that comes out and supplies vacuum to the EGR value when the computer tells the solenoid to open the EGR valve. Finally the DPFE sensor on the left of the motor, mounted to a bracket right by the rear spark plug, so it's just in front of the firewall, right below the blower motor the cabin heat / AC. It has an electronic connector and then two tubes... One connects down to the exhaust manifold and the other to the tube that goes into the back of the EGR valve.

and to replace the parts... They are about $80 each from Advance. The DPFE sensor was in-stock; They had to order the solenoid as a special order. There doesn't seem to be any way to test these components, which seems utterly crazy to me.

I still have not resolved my issue. I did test the EGR valve by starting up the truck and pulling the green vacuum line off of the top of the EGR valve, then putting a vacuum gauge on it, and pumping up the vacuum, which should open the EGR valve. The engine died (as it should) which indicates that the EGR functions when a vacuum is applied to it. That is saying to me that for some reason, the EGR isn't being activated like it should be. I've reved up the engine whilst under the hood, and I never sense the vacuum line being activated to open the EGR valve. I'm not 100% sure under what conditions the valve is supposed to open though, so it's hard to say if my "test" can be considered conclusive. Since I've replaced both the DPFE sensor and the soleoid, the only thing I can conclude at this point is that there is either something wrong with the ECM, or the wiring between the solenoid and the ECM is damaged. I prob. need to take mine somewhere and just cough up the $80 for the diagnostic.
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