Vacuum reservoir. Vehicle speed input

Vacuum reservoir


The vacuum reservoir is a plastic storage tank connected to an engine vacuum source by vacuum lines.


The vacuum reservoir is used to supply the vacuum needed to maintain proper speed control operation when engine vacuum drops, such as in climbing a grade while driving. A one-way check valve is used in the vacuum line between the reservoir and the vacuum source. This check valve is used to trap engine vacuum in the reservoir. On certain vehicle applications, this reservoir is shared with the heating/ air-conditioning system. The vacuum reservoir cannot be repaired and must be replaced if faulty.

Vehicle speed input


The Vehicle Speed Sensor (VSS) is no longer used for any Dodge Truck.

Vehicle speed and distance covered are measured by the Rear Wheel Speed Sensor. The sensor is mounted to the rear axle. A signal is sent from this sensor to the Controller Antilock Brake (CAB) computer.

A signal is then sent from the CAB to the Powertrain Control Module (PCM) to determine vehicle speed and distance covered. The PCM will then determine strategies for speed control system operation.

    Dodge Durango (DN) 1998-2003 Service Manual


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