Vehicle Speed Output

Powertrain Control Module - Vehicle Speed Output (PCM-VSO) speed signal subsystem generates vehicle speed information for vehicle's electrical/electronic modules and subsystems that require vehicle speed data. This subsystem senses transmission output shaft speed using a sensor. See OUTPUT SHAFT SPEED SENSOR  or VEHICLE SPEED SENSOR  under INPUT DEVICES. Vehicle speed data is processed by PCM and distributed as a hard-wired signal or as a multiplexed data message.

Key features of PCM-VSO system are to:

• Infer Vehicle Movement From Output Shaft Sensor Signal
• Convert Transmission Output Shaft Rotational Information To Vehicle Speed Information
• Compensate For Tire Size & Axle Ratio With A Programmed Calibration Variable
• Utilize Transfer Case Sensor For Four Wheel Drive Applications
• Distribute Vehicle Speed Information As A Multiplexed Message &/Or An Analog Signal

The signal from a non-contact shaft sensor mounted on transmission (OSS) or transfer case (TCSS) is sensed directly by PCM. PCM converts OSS or TCSS information to 8000 pulses per mile, based on a tire and axle ratio conversion factor. This conversion factor is programmed into PCM at time of vehicle assembly and can be reprogrammed in the field for servicing changes in tire size and axle ratio. PCM transmits computed vehicle speed and distance traveled information to all vehicle speed signal users.

VSO information can be transmitted by a hard-wired interface between vehicle speed signal user and PCM, or by speed and odometer Standard Corporate Protocol (SCP) multiplexed data messages. VSO hard-wired signal wave form is a DC square wave with a voltage level of zero to battery voltage. Typical output operating range is 2.22Hz per MPH. Multiplexed data for speed and distance data are transmitted as separate SCP messages over SCP multiplex link.