Their are two types of PCM outputs, device outputs and
output signals. Device outputs are components that the PCM controls their
function as either ON / OFF or with a Pulse Width Modulated signal that
can vary the components operation. Output signals are used by the PCM to
communicate certain operating conditions with other modules in the vehicle.
Output signals can also be ON / OFF or PWM type signals. The PCM typically
controls both the device outputs and the output signals by completing the
ground path of the circuit. Most outputs are monitored for failures and
will set a DTC. A scan tool can also command most of the outputs ON in order
to diagnose failures.
PCM device outputs include the following:
| • | The EVAP Purge Solenoid. |
| • | The Idle Air Control valve. |
| • | The A/C Compressor Clutch relay. |
| • | The Cooling Fan relays. |
| • | The transmission solenoids. |
PCM output signals include the following:
| • | Delivered Torque output |
| • | Engine Speed (Tach) output |
