Part 2A
HEATING & A/C SYSTEMSystem Availability
- Depending on the model, either a Manual Temperature Control (MTC) or Automatic Zone Control (AZC) HVAC system is available in these vehicles.
System Controls
Manual Temperature Control (MTC)
- Refer to the Service Manual for MTC system description and operation information.
The Automatic Zone Control (AZC) Module:
- is fully addressable with the DRB III.
- communicates over the Programmable Communication Interface Multiplex System (PCI) Bus.
- has dual infrared sensors, mounted in the AZC module face, which independently measure surface temperature to maintain occupant comfort levels.
- has dual-zone temperature-controls to provide a wide side-to-side variation in temperature to meet the needs of either front seat occupant.
- can be operated in a manual mode.
- uses engine temperature data, received over the PCI Bus, for cold engine blower lock-out.
- uses engine RPM data, received over the PCI Bus, for wide-open throttle A/C cut-out.
- uses vehicle speed data, received over the PCI Bus, to determine air-flow over the condenser for optimum cooling performance.
- uses Evaporator Temperature Sensor data, received over the PCI Bus, to prevent evaporator freeze up while maintaining optimum cooling performance.
- uses Ambient Temperature Sensor data, received over the PCI Bus, to optimize comfort control.
- provides an A/C request to the BCM when compressor operation is desired.
- controls rear defogger operation.
- controls fan speed, providing 10 blower speeds in manual mode and infinite speeds in automatic mode.
- The Blower Motor Controller provides a 5.0 volt signal to the AZC Module over the Blower Motor Control circuit. The AZC Module provides a variable duty cycle ground to the 5.0 volt signal based on input from the blower switch. When the blower switch is set to LO speed, the AZC Module provides a short duty cycle (less time grounding the signal voltage). As higher blower speeds are requested, the AZC Module increases the duty cycle (more time grounding the signal voltage). When the blower switch reaches HI speed, the duty cycle increases to where the signal pattern is almost a flat line (with brief voltage spikes).
- 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 AZC 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 AZC 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.
- Refer to the Service Manual for additional AZC system description and operation information.
The Dual-Zone AZC HVAC system uses:
- two, two-wire electronic blend door actuators.
- one, two-wire electronic mode door actuator.
- one, two-wire electronic recirculation door actuator.
System Revisions
The 2002 WJ/WG HVAC systems remain mostly carryover from 2001. Revisions to the 2002 MTC and AZC HVAC systems include:
- the addition of an Evaporator Temperature Sensor which is hard wired to the BCM. Data from the sensor is used to prevent evaporator freeze up while maintaining optimum cooling performance.
- new Diagnostic Trouble Codes (DTCs) for a short low and for an open on the Evaporator Temperature Sensor circuit.
System Diagnostics (MTC)
Fault detection is through Diagnostic Trouble Codes (DTCs)
- DTCs are displayed by the DRB III.
- DTCs pertaining to the Evaporator Temperature Sensor are stored in the BCM. Diagnostics for these DTCs can be found in the Heating & A/C category of this manual.
- Diagnostics for symptoms pertaining to A/C compressor operation can be found in the Heating & A/C category and in the Powertrain Diagnostic Procedures manual.
- DTCs pertaining to A/C compressor control circuits are stored in the PCM/ECM. Diagnostics for these DTCs can be found in the Powertrain Diagnostic Procedures manual
- Refer to the Service Manual for additional MTC system diagnosis and testing information.
System Diagnostics (AZC)
Fault detection is through active and stored Diagnostic Trouble Codes (DTCs)
- DTCs are displayed by the DRB III.
AZC Module DTCs
- Active DTCs are those which currently exist in the system. The condition causing the fault must be repaired in order to clear this type of DTC.
- Active DTCs become stored DTCs when the condition that caused the active DTC no longer exists.
- Stored DTCs will be erased after 72 key cycles or by clearing them with the DRB III.
- Diagnostics for symptoms pertaining to A/C compressor operation can be found in the Heating & A/C category of this manual and in the Powertrain Diagnostic Procedures manual.
- Refer to the Service Manual for additional AZC system diagnosis and testing information.
BCM DTCs
- DTCs pertaining to the Evaporator Temperature Sensor are stored in the BCM. Diagnostics for these DTCs can be found in the Heating & A/C category of this manual.
PCM/ECM DTCs
- DTCs pertaining to A/C compressor control circuits are stored in the PCM/ECM. Diagnostics for these DTCs can be found in the Powertrain Diagnostic Procedures manual.
Following A Repair (AZC)
The AZC Reset Module function:
- is actuated with the DRB III.
- must be actuated if the AZC Module or any door actuator is replaced.
- homes and repositions door actuators.
BODY CONTROL MODULE
The Body Control Module (BCM) supplies vehicle occupants with visual and audible information and controls various vehicle functions. To provide and receive information, the module is interfaced to the vehicle's serial bus communication network (Programmable Communication Interface or PCI bus). This network consists of the Powertrain Control Module (PCM) or Engine Control Module (ECM) (diesel), the Memory/Heated Seat Module (MHSM, MSM or HSM), the Sentry Key Immobilizer Module (SKIM), the Transmission Control Module (TCM), the Electro/Mechanical Instrument Cluster (MIC), the Driver Door Module (DDM), the Passenger Door Module (PDM), the Airbag Control Module (ACM), the Controller Antilock Brake (CAB), the optional Electronic Vehicle Information Center (EVIC), the optional PCI radio, the optional CD changer, the optional Automatic Zone Control Module (AZC), the shifter assembly (diesel), the optional power amplifier, the optional adjustable pedal module, the optional rain sensor, and the optional intrusion transceiver module (export). The BCM is operational when battery power is supplied to the module and in addition, ignition switch power is needed for ignition switched functions.
The BCM provides the following new features:
- Full control of all exterior and interior lamps, including these features:
- A Battery Saver automatically turns OFF all exterior and interior lamps within 8 minutes after the ignition is turned OFF, if they are not turned OFF by the driver. This includes the front and rear reading/courtesy lamps and the cargo area dome lamp, even if they are turned ON manually.
- Theater-style interior lighting dims gradually when the doors are closed.
- Interior courtesy lamp operation may be "defeated" using the dimmer control ring on the left multifunction switch.
- Instrument panel light intensity may be maximized for daytime visibility with the head lamps or parking lights by using the dimmer control ring on the left multifunction switch.
- An Accessory/Sunroof Delay allows continued operation of the sunroof and the power windows after ignition-OFF. These accessories can be operated up to 45 seconds after ignition-OFF or until door is opened.
- Beep tones for warnings and programming actions associated with the Sentry Key Immobilizer system and the EVIC.
The BCM also provides the following features:
- Intermittent wipe and low speed wiper control
- Wiper system status
- Ignition ON/OFF timer
- VF displays synchronization
- Rear door and liftgate ajar status
- Acquisition & transmission of external temperature
- A/C select switch status
- Chime
- Courtesy lamps with fade to OFF feature
- Reading lights/glove box lamp load shedding control
- Exterior lighting control including automatic headlamps, fog lamp control, rear fog lamp control and parking lamps
- Exterior lamp status
- Headlamp time delay upon ignition OFF and head-lamps switch OFF
- Parade mode
- Illuminated entry
- Instrument panel dimming
- Vehicle theft security system with panic & horn and hazard lamp activation
- Key-in ignition switch interface
- Brake fluid level switch/park brake switch interface
- Seatbelt reminder
- Speed sensitive intermittent wipe control
- Remote radio switch interface to radio
- Vehicle ignition status
- BCM self diagnostics
- Liftgate courtesy lamp disable
- Rear window defogger control
- Accessory delay control (windows and sunroof)
- Fuel economy and Distance To Empty (DTE) calculations
- Heated seat switch status
- Exterior lamp load shed
- Support of EVIC programmable features
The BCM receives information over the PCI bus from the PCM in order to support certain features.
The required information is as follows:
- Engine RPM
- Engine and battery temperature
- Injector on time and distance pulses
- Vehicle speed
- Engine model
- Fuel tank level
- Vehicle identification number
The BCM provides the PCM with information on the A/C switch status.
The 2002 WJ/WG has several programmable features which can be enabled/disabled by using the EVIC or the DRB III.
CHIME SYSTEM
The chime system responds to requests from five modules: the Body Control Module (BCM), Electronic Vehicle Information Center (EVIC), Mechanical Instrument Cluster (MIC), Sentry Key Immobilizer Module (SKIM) and the Powertrain Control Module (PCM). Each module monitors its related systems and, via the PCI bus, requests the BCM to sound its internal chime as needed.
The chime will sound for the following conditions:
MIC Requested Chime Messages
- Airbag
- Check Gauges: Charging Voltage Low
Coolant Temp High
Low Oil Pressure
Charging Voltage High
- Low Fuel
- ABS
- Low Battery Voltage
- Water in Fuel (Diesel)
- Low Coolant level (Diesel)
BCM Initiated Chime Messages
- Headlamp ON with ignition OFF and driver door open
- Key in ignition with ignition OFF and driver door open
- Seat Belt Warning
- Overspeed Warning (Gulf Coast Countries Only)
EVIC Chime Requested Messages
When the following messages are displayed the EVIC will send a chime request to the BCM. The BCM will respond with a series of chimes.
- Turn signal ON for more than 1.0 mile
- Service reminder
- Coolant level low
- Washer fluid low
- Tire Pressure Monitoring System alert messages (if equipped)
- Door or liftgate ajar (when critical speed is reached)**
**CRITICAL SPEED CHART
Sentry Key Immobilizer System
The Sentry Key Immobilizer System (SKIS) also uses tactile beep support from the chime warning system. The Sentry Key Immobilizer Module (SKIM) is programmed to send chime request messages over the Programmable Communications Interface (PCI) data bus to the Body Control Module (BCM) to provide audible confirmation that:
- the SKIM has been successfully placed in the Customer Learn mode.
- A new Sentry key transponder has been successfully programmed by the SKIM.
See the owner's manual in the vehicle glove box for more information on the features, use and operation of the SKIS. Refer to Sentry Key Immobilizer System in the Description and Operation of the service information - Vehicle Theft/Alarm systems for more information on the SKIS. For diagnostic information, refer to the Powertrain Diagnostic Information.
DOOR AJAR SYSTEM
The door ajar, liftgate ajar, and the liftgate flip-up ajar states are used as inputs for various control modules on the vehicle. The DRB III will display the state of the door ajar, liftgate ajar, and liftgate flip-up ajar switches in Inputs/Outputs. It's important to note, that when a door, liftgate, or liftgate flip-up is closed, the switch state on the DRB III will show OPEN, and when the door, liftgate, or liftgate flip-up is open, the switch state will show CLOSED. During diagnosis, if a door, liftgate, or liftgate flip-up is closed and the DRB III displays the switch state as CLOSED, it indicates a shorted ajar circuit. If the door, liftgate, or liftgate flip-up is open and the DRB III displays the switch state as OPEN, it indicates an open ajar circuit.
DOOR MODULES
A multiplexed door module is located on each front door, driver door (DDM) and passenger door (PDM). They control the following features: power door locks, automatic (rolling) door locks, driver window express down, memory recall functions (adjustable pedals, memory seats and mirrors), remote keyless entry, power mirrors, heated mirrors, door key cylinder disarm (driver door only), door lock inhibit and auto unlock on exit. Reduced wiring complexity is a key advantage of using multiplexed door modules. These modules are addressable with the DRB III from the "Body" menu to facilitate faster and easier diagnosis.
Power Windows
The power windows can be raised or lowered from the driver's door module (DDM) or the individual door switch. The DDM has a lock out switch that prevents the windows from being operated from any switch except the driver's door. When the switch is pressed, it also shuts OFF the individual door switch LED's.
A feature of this system allows the windows to be operated from any window switch for 45 seconds after the ignition is turned OFF, provided a front door is not opened. Another feature is the "Express Down" driver door only. When the driver presses the down switch to the second detent, the window will travel all the way down even if the switch is released. To stop the window travel, simply press the switch momentarily in either direction.
Twelve volts are provided on the rear window motor circuit on both the up and down circuits. The appropriate door module supplies this voltage. When the rear switch is pressed, the supply circuit to one side of the switch is opened and ground is provided making a complete circuit and therefore operating the window motor.
Power Door Locks
The power door locks are operated four different ways:
1. Front door lock switches
2. Auto (rolling) door lock feature (vehicle speed above 15 MPH (24 kmh) and all doors closed).
3. Auto unlock on exit (vehicle stopped after auto door locks had locked the doors, transmission in neutral or park and the drivers door is opened - all doors will unlock).
4. Remote Keyless Entry (RKE)
Door Lock Inhibit
When the key is in the ignition and in the OFF position, and either front door is opened, the lock switch on that door is disabled. The unlock switch is still functional. This protects against locking the vehicle with the keys still in the ignition. For example, if the driver's door is opened and the passenger front door closed, the locks are operational from the passenger door switch.
Remote Keyless Entry
When the lock button on the transmitter is pressed, all locks will lock, illuminated entry will be turned OFF, (providing all doors are closed) and the vehicle theft security system (if equipped) will be armed. When the unlock button on the transmitter is pressed one time, the driver front door will unlock, the illuminated entry will turn ON the courtesy lamps, the vehicle theft security system (if equipped) will be disarmed. When the button is pressed a second time, the other doors will unlock. This feature is programmable to open all doors on one press using the EVIC or the DRB III.
The passenger door module (PDM) contains the RKE receiver. When the PDM receives a valid signal from the RKE transmitter, it will send a signal on the PCI bus to lock or unlock the doors. The RKE transmitter uses radio frequency signals to communicate with the RKE receiver. If vehicle is equipped with the memory system, the memory message will be received as to which transmitter sent the signal (1 or 2).
Panic Function
When the panic button on the RKE transmitter is pressed it pulsates the headlamp, hazard lamps and horn relays and actuates the courtesy lamp relay. By pressing the button again the horn and exterior lamps will stop but the courtesy lamps will remain ON until the BCM times them out or the ignition is turned ON. The panic feature is able to be set if the ignition is ON but only if the panic button is pressed prior to the vehicle being started, it will continue for three minutes or until the vehicle has reached a speed of 15 MPH, if not canceled by the operator.
Actuating the headlamp, horn, hazard lamps and courtesy lamp relays with the DRB III will verify that the circuits and the body control module are OK. If the panic feature is still inoperable with both transmitters, replacement of the passenger door module will be necessary. If the function is inoperable with just one transmitter, then it is obvious that the transmitter must be replaced.
Rolling Code
The rolling code feature changes part of the transmitter message each time that it is used. The transmitter message and the receiver message increment together. Under certain conditions with a rolling code system (pressing a button on the RKE transmitter over 255 times outside the receiver range, battery replacement, etc.), the receiver and transmitter can fall out of synchronization.Note: The lock function works from the RKE keyfob even in out of synchronization condition and therefore it could be verified by pressing the LOCK button on the RKE keyfob. To re-synchronize, press and release the UNLOCK button on the RKE keyfob repeatedly (it may take up to eight cycles) while listening carefully for the power door locks in the vehicle to cycle, indicating that re-synchronization has occurred.
Programmable Door Lock Features
- The RKE can be changed to unlock all doors with one press
- The Automatic Door Locks can be enabled/ disabled
- Auto Unlock on Exit can be enabled/disabled
- RKE horn chirp on lock can be enabled/disabled
- RKE optical chirp (turn signal lamps) can be enabled/disabled
- Program a new RKE transmitter (DRB III only)
- RKE linked to memory (if equipped with memory system) enabled/disabled (DRB III only). Allows memory to be operable only from the driver door switch.