Circuit Description

This test checks for an EGR system malfunction. EGR operation will cause variations in MAP sensor because when EGR valve opens, exhaust gas is drawn through it with intake manifold vacuum. When all test enable conditions are met, the test begins with PCM cycling the EGR from off to on and on to off, and recording the change in MAP. The PCM then calculates the MAP error, or the difference between actual MAP change and the MAP change that the PCM expected to see. The PCM performs this test several times to gain an average. If at least 6 tests have occurred, the PCM compares its current average MAP error to the failure limit. If the average MAP error is 4 kPa or greater, DTC will set. If the error is less than the limit, EGR operation is returned to normal software control.