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Vehicle Speed Sensor: Description and Operation

PURPOSE
The Programmable Speedometer/Odometer Module (PSOM) provides a vehicle speed signal input to:
- Powertrain Control Module (PCM)
- Speed Control Servo Amplifier
- Instrument Cluster

The speed signal is used by the PCM to determine transmission shift points and torque converter clutch operation.

OPERATION
The PSOM receives a vehicle speed signal from the Differential Speed Sensor (DSS) on pin 4 DSS input, and pin 5 DSS return. It converts this signal to a standard 8000 pulses-per-mile speed signal output. This output signal is sent to the PCM on pin 3 PSOM (+) and pin 6 PSOM (-).

The PSOM receives two power supply inputs. Pin 1 receives a continuous 12.0 volt input while pin 2 receives a 12.0 volt input only when the ignition switch is in run.

RELATED DIAGNOSTIC TROUBLE CODES

DTC 29/452 PCM detected an error in the PSOM output signal.
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