STRIP 4V3303 - Caterpillar

Illustration 1 g03395105
Parking brake circuitThe components of the parking brake circuit are the: parking brake switch, transmission oil pressure sensor, brake accumulator oil pressure sensor, parking brake oil pressure sensor, parking brake solenoids, instrument cluster, parking brake indicator and Power Train Electronic Control Module (ECM).
Illustration 2 g03338617
Dash panel (1) Parking brake switch
Illustration 3 g03395118
(2) Instrument cluster (3) Parking brake indicator
Illustration 4 g03395128
(4) Transmission oil pressure sensor
Illustration 5 g03395130
View of parking brake control valve (5) Parking brake oil pressure sensor (6) Parking brake solenoid 1 (7) Parking brake solenoid 2
Illustration 6 g03338616
Cab (8) Power Train ECM
Illustration 7 g03395129
(9) Brake accumulator oil pressure sensor
Illustration 8 g03511737
Cab (below rear arm rest) (A) Circuit breaker panel coverThe relays are located in the circuit breaker panel. The circuit breaker panel is located under the right side armrest behind cover (A).
Illustration 9 g03528836
Circuit breaker panel (cover removed) (10) Circuit breaker 22 (11) Circuit breaker 24With the key start switch in the ON position, 24 V power is supplied via circuit breaker CB24 (11) to the Power Train ECM. 24 V power is supplied via circuit breaker CB22 (10) to the Instrument Cluster.Parking brake control valve solenoids (6) and (7) are de-energized by moving parking brake control switch (1) to the ON position. Parking brake control valve solenoids (6) and (7) are de-energized by moving the engine start switch key to the OFF position.When parking brake switch (1) is moved to the ON position, 24 V power will be interrupted to:
Parking brake solenoid 1 (6)
Parking brake solenoid 2 (7) The pressure oil in the wheel brakes is returned to the hydraulic tank and the parking brake is engaged. In this condition, parking brake oil pressure sensor (5) sends a signal to Power Train ECM (8). Power Train ECM (8) sends a signal via the CAN Data Link to instrument cluster (2). Instrument cluster (2) turns on parking brake alert indicator (3) .When key start switch is in ON position and parking brake switch (1) is in OFF position, parking brake switch (1) must be cycled to allow parking brake to dis-engage.When oil pressure decreases in service braking system, a PWM signal is sent from brake accumulator oil pressure sensor (9) to Power Train ECM (8). Power Train ECM (8) de-energizes parking brake solenoids (6) and (7). De-energizing the parking brake solenoids will engage the parking brake.When the oil pressure decreases in the transmission, a PWM signal is sent from transmission oil pressure sensor (4) to Power Train ECM (8). Power Train ECM (8) de-energizes the parking brake solenoids. De-energizing the parking brake solenoids will engage the parking brake.When parking brake switch (1) is moved to the OFF position, power from Power Train ECM (8) is supplied to energize the parking brake solenoids. Energizing parking brake solenoids (6) and (7) will allow pressure oil to flow to the wheel brakes to disengage the parking brake. Parking brake alert indicator (3) will be off.ReferenceFor more information on the