Vehicle Speed Control

The Powertrain Control Module (PCM) operates the vehicle speed control system. The vehicle speed control switches are located in the steering wheel, below the airbag.

Circuit V34 from fuse 18 in the fuse block supplies battery voltage to the vehicle speed control ON/OFF switch. Circuit A21 supplies voltage to fuse 18 when the ignition switch is in the START or RUN position. In the START or RUN position the ignition switch connects circuit A21 with circuit A1. Fuse 7 in the Power Distribution Center (PDC) protects circuit A1.

The vehicle speed control ON/OFF switch supplies voltage to the SET/COAST and RESUME/ACCEL switches. Both switches send signals to the PCM which supplies the ground path for the switches. The SET/COAST and RESUME/ACCEL switches have internal resistors that drop the voltage level. Also, the PCM is programmed with the acceptable voltage ranges for the signals from each switch.

The PCM controls the vent and vacuum functions of the vehicle speed control servo on circuits V35 and V36. Depending on the signal it receives from vehicle speed control switches, the PCM either applies vacuum to or vents vacuum from the servo. Circuit V36 from cavity 33 of the PCM sends the vacuum signal to the servo. Circuit V35 from cavity 53 sends the vent signal.

Circuit V32 signals to the PCM that the speed control switch is in the ON position. The V32 circuit connects to cavity 49 of the PCM. Circuit V32 also connects to the stop lamp switch.

In the closed position, the stop lamp switch connects circuit V32 with circuit V30 to power the vehicle speed control servo. Circuit Z1 provides ground for the vehicle speed control servo.

Circuit V31 provides the SET/COAST signal to cavity 48 of the PCM. Circuit V33 sends the RESUME/ ACCEL signal to cavity 50 of the PCM.

Circuit V40 connects to cavity 29 of the PCM and to ground through the stop lamp switch. When the stop lamp switch opens, voltage is removed from the servo on circuit V30 and the PCM vents the servo. From the stop lamp switch, circuit Z1 provides ground for circuit V40.