CONTROL FUNCTIONS (CONT’D) General (Cont’d) EGR valve output The EGR valve output is a high-side output as shown in [Figure 10-40-13] The EGR valve is driven by a stepping motor. This stepping motor adopts two-phase excitation and requires holding current to keep the valve stopped. "Two-phase excitation" means that the solenoid is supplied with two-phase current and "holding current" does that the solenoid is always energized. The motor of the EGR valve is consequently approx. 24 watt (12 watt x 2 phase) heated even while the engine is at rest be warned that touching it could burn you. The E-ECU turns on or off the output transistors in the sequence shown in [Figure 10-40-13], thereby driving the solenoids for the stepping motor and opening/closing the EGR valve. In the EGR valve, the full-close position is 0 step and the full-open position is 54 steps.
Figure 10-40-13 VB
ECU
Motorized valve operation
A
Open (counterclockwise) Step
VB
A A
A VB
A B B
B
B VB B
A EGR valve motor (Stepping motor)
B Close (clockwise) Step A A B B
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E55W, E60, E80 Electronic Control System Manual
