RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
he headlamp switch is a direct input to the instrument cluster which is sometimes known as the Cab Control Node (CCN). The instrument cluster sends a
Programmable Communications Interface (PCI) bus message to the FCM informing it of a headlamp switch status change. The FCM then turns power
ON or OFF (depending on the bus message) to the headlamps through four "fuseless" circuits. These circuits are electronically controlled and
continuously monitored for malfunctions. Power is supplied to each filament in a separate circuit. For vehicles equipped with Daytime Running Lamps
(DRL), the FCM electronically steps down the headlamp voltage to provide the desired illumination levels.
Washer Pump Motor
The washer switch is a direct input to the instrument cluster. The instrument cluster sends a PCI bus message to the FCM informing it of a request to
wash. The washer pump motor is then powered through low side control inside the FCM.
This circuit is electronically controlled and continuously monitored for malfunctions. In addition, the FCM electronically protects the washer pump
motor from system voltages higher than 16 volts by automatically switching OFF the low side circuit. The low side circuit is connected to pin 45 in the
FCM connector.
If the FCM receives a prolonged request to wash lasting 30 seconds or more, it will treat the request as a stuck switch condition and deactivate the
washer pump motor. The FCM will not reactivate the washer pump motor until there is at least a two second break in the request to wash from the
instrument cluster.
Relay Controls
Accessory Relay
The accessory relay works in conjunction with the FCM's power accessory delay features to control the operation of the radio, power windows, washer
pump motors, wiper motor and power outlets. The accessory relay is turned ON by the FCM through the relay's low side control circuit. This circuit is
electronically controlled and continuously monitored for malfunctions.
Depending on the ignition switch position, the accessory relay will remain ON or will time out and deactivate. The accessory relay remains ON in the
RUN and ACCY ignition switch positions. In the UNLK and OFF positions, the relay will remain energized for 45 seconds and then deactivate. During
this time-out period, if a driver or passenger door is opened, the relay will be deenergized immediately. While the ignition switch is in the START
position, the relay will also drop out and then resume operation. Accessory relay operation is most noticeable by observing the operation of the radio.
Adjustable Pedals Relay
If equipped, the adjustable pedals relay, when not activated, supplies fused battery power to the adjustable pedals switch. If the FCM receives a bus
message that the vehicle is in reverse or that the cruise control is engaged, it will apply a ground to the adjustable pedals relay control circuit. The ground
will activate the relay which will open the power circuit to the adjustable pedals switch. The relay control circuit is continuously monitored for
malfunctions which the FCM will report as DTC's.
Fog Lamp Relay
If equipped, the fog lamp switch is a direct input to the instrument cluster. The instrument cluster sends a PCI bus request to the FCM to turn ON the fog
lamp relay. The fog lamp relay is then actuated by the FCM through low side control. This circuit is electronically controlled and continuously monitored
for malfunctions. The FCM "learns" that the vehicle is equipped with fog lamps by reading the instrument cluster PCI bus message.
Horn Relay
The Horn Relay, which is internal to the IPM, is controlled by the FCM through PCI bus messages from the instrument cluster. These bus messages will
be sent when either the horn switch is pressed which is hard wired to the instrument cluster, panic mode is requested from the RKE or for vehicle theft
security reasons (if equipped). Under normal operating conditions, if the horn is activated for more than 30 seconds, the FCM will automatically
deactivate the horn to prevent damage. The FCM will reactivate control of the relay after a 25-second cool-down period. The relay control circuit is
continuously monitored for malfunctions that the FCM will report as DTC's.
Park Lamp Relay
The park lamp switch is a direct input to the instrument cluster. The instrument cluster sends a PCI bus request to the FCM to actuate the park lamp
relay. The park lamp relay is then actuated through the low side control circuit. This circuit is electronically controlled and continuously monitored for
malfunctions.
Wiper High/Low Relay
The wiper switch is a direct input to the instrument cluster. The instrument cluster sends a PCI bus request to the FCM to actuate the wiper high/low
relay. The relay switches power between the low speed and high speed brush of the wiper motor. The wiper high/low relay is then actuated through the
low side control circuit. This circuit is electronically controlled and continuously monitored for malfunctions.
Wiper ON/OFF Relay
