Circuit Description

The engine control module (ECM) performs a insufficient flow test on the exhaust gas recirculation (EGR) system during deceleration and an excessive flow test during engine crank.

The insufficient flow test is when the ECM momentarily commanding the EGR valve to open while monitoring the signal of the manifold absolute pressure (MAP) sensor and the EGR position sensor. If the MAP signal is incorrect for the EGR pintle position, the ECM records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow tests required to exceed the fail threshold may vary according to the amount of detected EGR flow error. The ECM will only allow one EGR flow test during an ignition cycle. Following a code clear event, the ECM will perform multiple EGR flow tests.

The excessive flow test is when the ECM monitors the position of the EGR valve during engine crank. The EGR valve should not be open during engine crank.