Turning EGR on and Off
Turning EGR OnWhen all of the conditions have been met to enable EGR, the PCM calculates the desired pintle position and determines the rate at which it will open or ramp the pintle to its desired position. The ramp rate depends on vehicle speed, A/C clutch status, and outside air temperature. The PCM controls the ramp rate by varying the EGR solenoid duty cycle. The ramp rate is a percentage of desired pintle position and is determined as follows:
^ If the vehicle speed is greater than 20 mph, the pintle will open at a rate of 5% every 0.05 second.
^ If the vehicle speed is less than or equal to 20 mph, A/C clutch engagement is not possible, and outside air temperature is at least 41°F, the pintle will open at a rate of 2.3% every 0.05 second.
^ If the vehicle speed is less than or equal to 20 mph, A/C clutch engagement is possible or outside air temperature is less than 4°F, the pintle will open at a rate of 0.8% every 0.05 second.
The PCM will maintain the same ramp rate until the desired pintle position is reached. When EGR is being ramped on, the PCM will maintain current spark advance. The PCM will ramp the spark to its desired advance once EGR has reached its desired position. This delay is necessary because EGR does not reach all cylinders immediately, and premature spark advance would cause driveability problems.
Turning EGR Off
When EGR is turned off, the PCM will cause the pintle to close at a rate of 6.3% every 0.05 second until the pintle is in the closed position. However, if engine speed is 0 RPM (engine not running), the pintle will be immediately closed.
If EGR status transitions from off to on or on to off during a ramp, the ramp will reverse directions from that point and continue at the normal rate until the desired pintle position is reached.