Cherokee 4WD L6-242 4.0L VIN S MFI (1992)
Vehicle Speed Sensor: Description and Operation
Vehicle Speed Sensor (typical)
LOCATION
The vehicle speed sensor is located in the extension housing of the transmission (2WD), or the extension housing of the transfer case (4WD).
PURPOSE
Sensor is used to inform engine controller of vehicle speed, vehicle acceleration, or deceleration.
OPERATION
Sensor generates 8 voltage pulses per axle shaft revolution (sent directly to engine controller).
Engine controller uses sensor input with input from Throttle Position Sensor (TPS) to determine closed throttle deceleration or closed throttle idle
(vehicle stopped).
During idle, (no signals being received from sensor), engine controller actuates Automatic Idle Speed (AIS) motor to maintain desired engine idle
speed.
During closed throttle deceleration, (slower signals received from sensor), engine controller actuates AIS motor to maintain desired Manifold
Absolute Pressure (MAP) sensor value.
The vehicle distance (speed) sensor input signal is also used as a mileage reference for the Emissions Maintenance Reminder Light (EMR), and
also to maintain speed control operation.
