Does it have DPFE ( Differential Pressure Feedback EGR) EGR positioning sensor
The computer gets a sensor input to activate the solenoid to transfer vacuum to the EGR-
When you apply direct vacuum it opens-good-check the solenoid/vacuum hoses going to it and out from it while slowly accelerating to 2k rpm-it should have vacuum going to the EGR.
The purpose of the EGR is to recirculate the exhaust gases back to the engine to be reburn that way it lowers the combustion temperature and prevent the formation of oxides of nitrogen.
NOX failures are usually EGR-related, since the EGR system is primarily responsible for reducing oxides of nitrogen. But NOX emissions can also be caused by a bad three-way converter or a computer control system that remains in open loop
Thursday, April 12th, 2007 AT 9:00 PM