[Tech II]

Usually, when the car is at normal operating temp, and during a DECEL, the ECM will command the EGR SLIGHTLY open, and then look for a change in MAP reading......if it doesn't see this, a code 75, 76, or 77 is set(not sure which one)......more often than not, it's not an EGR problem......the problem is the upper plenum......the passageway in the upper plenum from the EGR, gets crudded up over time, and because during the test, the EGR is commanded open very slightly, the MAP can't "sense" the change in vac......sometimes just cleaning out the passage takes care of it.....a bi-directional scan tool would be needed to check the individual coils to see if the EGR is functioning properly....