DESCRIPTION & OPERATION
| WARNING | To avoid injury from accidental air bag deployment, read and follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in AIR BAG RESTRAINT SYSTEM article in the ACCESSORIES/SAFETY EQUIPMENT section. |
Note. Powertrain Control Module (PCM) may also be known as Vehicle Control Module (VCM).
To provide improved idle quality, improved Wide Open Throttle (WOT) performance and A/C system protection, the A/C compressor clutch is controlled by the PCM.
For proper control of cooling fans, A/C compressor clutch and Idle Air Control (IAC) valve, a refrigerant pressure sensor is used. PCM uses signal provided by sensor to monitor high and low side refrigerant pressures. If PCM detects a fault in refrigerant pressure circuit, A/C compressor clutch will be disabled.
The A/C compressor clutch relay is controlled by PCM. This allows PCM to raise idle speed before engaging compressor clutch, or disable compressor clutch during WOT, high engine RPM, high power steering loads and hot engine restarts. PCM also disables compressor clutch if coolant temperature becomes excessive.
Description
Powertrain Control Module (PCM) receives an A/C request signal from Body Function Controller (BFC) over CLASS 2 serial data line. When A/C is requested, PCM provides a ground path to A/C clutch relay control circuit. When relay circuit is grounded, A/C compressor clutch relay is energized. PCM delays grounding relay circuit for .3 second. This allows PCM to adjust engine idle RPM for additional load.
PCM will temporarily de-energize A/C compressor clutch relay for a hot engine restart, wide open throttle, engine RPM greater than 6000 RPM, or during Idle Air Control (IAC) valve reset. A/C compressor clutch relay will remain de-energized when a DTC P0530 is set, or when there is no A/C request signal to PCM.