Switch (Parking Brake)
N OT E
Normally Closed (N/C) and Normally Open (N/O) circuits are used for diagnostic
purposes. If the N/C and N/O circuits are ever in the same state, a circuit failure is present
and a diagnostic code for the ON/OFF pole is logged.
The parking brake switch is a four-pole double-throw rocker switch that is located under the left hand console. The
switch is actuated by a plunger that mechanically actuates the rocker switch. Two of the poles on the switch are not
used. The purpose of the two poles that are used is listed below:
"ON/OFF" This pole informs the ECM that the switch is ON or that the switch is OFF. When the switch is ON, the
ECM shifts the transmission to neutral and the ECM activates the left brake.
"BRAKE BACKUP" This pole provides the backup for the activation of the brake. When the switch is ON, the
brake backup pole activates the parking brake solenoid, which engages the left brake.
The parking brake switch applies the parking brake in two separate ways through the "ON/OFF" pole and the
"brake backup" pole.
The ON/OFF pole of the parking brake switch is an input of the ECM. The ON/OFF pole informs the ECM that the
operator wants the parking brake engaged. The ECM shifts the transmission to 1st Speed and the ECM activates
the left brake.
The ON/OFF pole has two input connections to the ECM. When the operator places the parking brake switch in the
ON position, the Normally Closed circuit is open and the Normally Open circuit is closed to ground. When the
switch is in the OFF position, the Normally Closed circuit is closed to ground and the Normally Open circuit is open.