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| Illustration 1 | g03668888 |
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View of the "Service Brake" pedal (Secondary Brake) (1) "Service Brake" pedal | |
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| Illustration 2 | g06412344 |
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View of the service foot brake control (1) Service Brake pedal (2) Foot brake valve (3) Sensor group (A) Exhaust port (Tank port) (B) Supply port (Pressure port) (C) Outlet port (Brake port) | |
The primary purpose of the Service Brake pedal is to provide an input signal that is required to perform a diagnostic test.
The "Service Brake" control pedal (1) is on the cab floor to the left of the primary brake pedal and retarding pedal. The Service Brake control pedal (1) is used as an alternative to the primary brake pedal. The secondary brake control pedal (1) should not be used as the primary brake. Push the secondary brake control pedal to engage the brakes. The amount of force applied to the brakes is proportional to the amount of force that is applied to the pedal.
When service brake pedal (1) is depressed, foot brake valve (2) routes the oil from the service brake accumulator to outlet port (C). Pilot pressure at port (C) actuates the brake control valve at both front and rear brake sections of the brake control valve. The brake control valve relays service brake pressure to the front and rear wheels.
When service brake pedal (1) is released, internal passages in foot brake valve (2) route the oil at brake port (C) to exhaust port (A) allowing the service brakes to be released. Supply port (B) is blocked when the pedal (1) is released.
The service brake pedal position sensor (3) sends a signal to the "Brake" ECM indicating service brake pedal position. The Brake ECM uses the pedal position signal to disengage the Anti-Rollback feature.