Cabin Heater

When the ignition is in Run, the FCM monitors the PCI bus for the Cabin Heater Activation request. The Automatic or Manual Temperature Control initiates this request only when all conditions for the Cabin Heater activation are favorable. The request carries the status bit that the FCM requires to activate its Cabin Heater Assist Control output. This output is a low side driver (coming from FCM pin 15) which supplies a ground signal to the Cabin Heater (pin 5). When the Cabin Heater receives this ground signal input, it interprets this as an activation signal. The FCM low side driver is also capable of diagnostic sensing. The driver will sense an open circuit when the driver is off, and will sense a short to voltage when the driver is on. The FCM will set DTCs for both of these types of faults. For additional information, refer to CABIN HEATER .