RE: What tells EGR valve to operate?
 

Well I was looking at all data and if you have the 2.0 I would really look into the manifold differential pressure sensor. Ford has something similar to that and its called a dpfe sensor. Also on fords I see a lot of p0401 and as long as the egr passage is clean, I'll replace the dpfe sensor and that usually fixes the dtc.

RE: What tells EGR valve to operate?
 

Sorry for the delay. I looked into a troubleshooting manual and wound up at the same place. The manifold pressure differerntial sensor. I'm going to locate this sensor and try to see if it might be dirty or something.

RE: What tells EGR valve to operate?
 

if you were to trigger the solenoid to open the egr you can check the fluctuation voltage of the mdp. if the mdp was the problem, why would it not throw a mdp code too?

RE: What tells EGR valve to operate?
 

Good question. No code there. I didn't trigger the solenoid with the motor running, though. I could only trigger it with the harness unplugged from the solenoid so as to apply and then remove the battery positive voltage. I could hear the solenoid actuating. I am pretty sure that the PCM is not removing the 12 volts from the solenoid to actuate it. 12v battery positive holds the solenoid closed and it is available in the plug.

There's a few troubleshooting tips for the MDP to check voltage at the back of the plug. If it doesn't change when the engine is revved, then it might be defective. I will eliminate this first.
Then on to the ECT sensor.

RE: What tells EGR valve to operate?
 

Well, I fixed it.

Today I traded the Lancer in on a 2008 Chevy 1500 Single Cab W/T 4WD.

The check engineer light is temporarily fixed until the next one.

RE: What tells EGR valve to operate?
 

Haha well thats one way to fix the cel.

RE: What tells EGR valve to operate?
 

this was like getting hooked on a tv show and just when you think you'll find out who shot JR the season ends:(

to be continued next year on the chevy forum....lol

good luck to you.

RE: What tells EGR valve to operate?
 

Sorry. The trade had nothing to do with the CEL. It was opportunity knocks. 7,000 dollars off on the selling price of the truck. I couldn't resist. I've always wanted a 4WD Chevy. I was really interested in finding the problem. As you can tell, I'm persistant if not too smart.

Thanks for the help, regardless. Good luck to you all in the future. See you at the Chevy forum.