RAM 3500 Truck 2WD V8-5.7L VIN D (2003)
Power Ground
Ground source for all FCM functions
Ignition Switch RUN or START Position Status
12 volt input to inform the FCM of the ignition switch status for related FCM functions.
PCI Bus
Approximately 7.5 volt input to allow the FCM to communicate with other modules on the PCI bus.
Wiper Park Switch
Ground input used to determine the park placement of the wipers. The ground is also used as feedback to the FCM to determine wiper operating
mode.
Washer Fluid Level Switch
Ground input from the washer fluid level switch which closes when washer fluid is low.
Battery (+) Connection Detection
12 volt supply used to monitor battery connection to the IPM. The battery connection to the IPM uses an internal switch to check integrity of the
connection and that the Connector Positive Assurance (CPA) is engaged. If the CPA is not properly engaged, a voltage is sent to the FCM to be
interpreted as an unseated connector which will set a Diagnostic Trouble Code (DTC).
Heating & A/C System
HEATING & A/C SYSTEM
System Availability
Depending on the model, either a Single-Zone or Dual-Zone HVAC system is available in these vehicles.
System Controls
The Heater Control Module:
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is fully addressable with the DRBIII.
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communicates over the Programmable Communication Interface Multiplex System (PCI) Bus.
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controls blower motor operation, providing four blower speeds (Low, M1, M2, & High).
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controls heated mirror operation (if equipped).
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controls electronic door actuator operation.
The A/C-Heater Control Module:
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is fully addressable with the DRBIII.
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communicates over the Programmable Communication Interface Multiplex System (PCI) Bus.
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uses input from the evaporator temperature sensor to prevent evaporator freeze up while maintaining optimum cooling performance.
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provides an A/C request to the Powertrain Control Module (PCM) over the PCI Bus when compressor operation is desired.
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controls blower motor operation, providing four blower speeds (Low, M1, M2, & High).
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controls heated mirror operation (if equipped).
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controls electronic door actuator operation.
A simplified control system for operation of the mode, recirculation, and temperature control actuators provides positive positioning without the
complexity of feedback from position sensors. The A/C-Heater Control Module knows the number of operating actuator revolutions required for full
door travel as well as the number of actuator commutator pulses per revolution. Using these parameters, the A/C-Heater Control Module runs the
actuator for the number of commutator pulses that correspond to the desired door position. To maintain accuracy, the system recalibrates itself
periodically at known zero and full travel conditions.
The Single-Zone HVAC system uses:
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one, two-wire electronic blend door actuator.
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two, two-wire electronic mode door actuators.
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one, two-wire electronic recirculation door actuator.
The Dual-Zone HVAC system uses:
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two, two-wire electronic blend door actuators.
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two, two-wire electronic mode door actuators.
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one, two-wire electronic recirculation door actuator.
System Revisions
The 2003 DR, HVAC system remains mostly carry over from 2002. Revisions to the 2003 HVAC system include:
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a heater only option for select vehicles
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a change in A/C mode switch status indicator operation when performing the A/C Cooldown test. Refer to The A/C Cooldown Test under System
Diagnostics for more information.
