S126 Drive Mode Select Switch

The S126 Drive Mode Select Switch is a momentary rotary knob with two switches and up to four indicators. At rest, the S126 Drive Mode Select Switch remains in a neutral position with both switches open. When rotated to the left or right, the corresponding switch is closed. When released, the rotary knob returns to the neutral position and both switch will again be open. The two switches are situated within a resistor ladder. The K20 Engine Control Module applies 5 volts to the resistor ladder, which also receives a constant ground. The K20 Engine Control Module monitors the signal voltage. The signal voltage is measured within the resistor ladder. As each switch is closed, current flows through a different number of resistors, changing the voltage drop across the resistors and changing the voltage monitored by the K20 Engine Control Module.