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 |
