Diagnostic Aids

Decel Exponentially Weighted Moving Average (EWMA) value is an average of the difference in expected MAP change and actual MAP change caused by opening EGR valve during deceleration. By driving vehicle to 60 MPH and decelerating to 20 MPH, it can be determined if EGR system is okay, partially restricted or fully restricted.

A negative number, less than -3 indicates system is functioning properly. A positive number indicates system is fully restricted and the expected amount of EGR flow is incorrect. A number that falls between -3 and +2 indicates system is partially restricted. The Decel EWMA value should always be -3 or less. If value becomes more positive, check for damaged EGR pipe, restricted EGR passage or defective EGR valve.