Service Engine Soon LIght "Code P0400" ?????
 

Any help would be greatly appreciated.

I have a 96 Camaro Z28 and the Service Engine Soon light came on,
I work at a import car dealer and one of the mechanic used a scan tool and pulled the code P0400 EGR System Malfunctionm, not being a import they are unsure what this could be ( is too rich, too lean etc.)
The forum has always been very helpful when I owned my Corvette so I figured maybe some one might have some helpful information.

Thanks again :seeya

Re: Service Engine Soon LIght "Code P0400" ????? (Rome856)
 

My bet goes to a bad EGR solenoid valve (not activating to supply vacuum to the EGR valve) or a bad EGR valve itself.

I had this code intially when I first got my car. A Mity-vac test on the EGR valve showed the diaphram to be bad. Quick replacement and all was good.

You need to see if you're getting a vacuum signal to the EGR valve. If true then check the EGR valve itself.

That should be a good starting point.

Re: Service Engine Soon LIght "Code P0400" ????? (Rome856)
 

The quick way to diagnose this - clear the code. then, start the car. If the code comes back immediately, then its the control valve, if it takes a while, its the EGR itself.

you see, the computer will sence a bad control valve during initial self test at startup, but it won't find the EGR until it goes into closed loop...