A/C Signal: Description and Operation
DESCRIPTIONThis signal is sent from the A/C amplifier. When the A/C compressor is engaged, the A/C amplifier sends a signal to the Powertrain Control Module (PCM) to inform it that the A/C compressor is operating. This additional load on the engine requires a higher idle speed. The PCM will open the Idle Air Control (IAC) valve to create a lean condition. At the same time, it will also adjust the air/fuel mixture to compensate for the lean condition. This will increase the idle speed slightly to prevent stalling during A/C system operation.