Circuit Description

PCM contains Output Driver Modules (ODMs) that provides 7 switchable ground outputs for operating solenoids, relays, indicator lights, and other devices. Each of these ground outputs has fault lines that feed back to the PCM's microprocessor. When the output is off, the output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is on, it should receive zero volts, since it is grounding the output. If PCM sees zero volts when the output is off or 12 volts when the output is on, it sets a fault line low.

DTC P1642 is used to monitor the fault line of the vehicle speed output signal circuit. The Instrument Panel Cluster (IPC) sends 12 volts on the vehicle speed output circuit to the PCM. The PCM sends a pulse width modulated signal that the IPC, cruise control module and Remote Accessory Control (RAC) module use to determine vehicle speed.