Part 3A
INTERIOR LIGHTINGCourtesy Lamp Control
The body controller has direct control over the majority of the vehicle's courtesy lamps. The body computer will illuminate the courtesy lamps under any of the following conditions:
1. Any door is ajar.
2. The courtesy lamp switch on the instrument panel is closed.
3. A Remote Keyless entry unlock message is received. If the interior lamps are left ON after the ignition is turned OFF, the BCM will turn them OFF after 1 hour or until either the dome lamp switch or door ajar switch changes state.
Illuminated Entry
Illuminated entry will be initiated when the customer enters the vehicle by unlocking the doors with the key fob, or with the key if the vehicle is equipped with vehicle theft alarm. Upon exiting the vehicle, if the lock button is pressed with a door open, illuminated entry will cancel when the door closes. If the doors are closed and the ignition switch is turned ON, the illuminated entry also cancels.
MECHANICAL INSTRUMENT CLUSTER
The instrument cluster displays four gauges, a Vacuum Fluorescent (VF) odometer, a VF PRNDL and up to (18) indicators. One reset button is used to switch the display from trip to total. Holding the button when the display is in the trip mode will reset the trip mileage. The cluster also supplies the power for the panel illumination. Most of the information that is displayed is received over the PCI bus from several modules.
With ignition in "lock", the cluster will wake up and display the door ajar and odometer display when a door is opened. The cluster will also wake up to control the panel illumination. In "OFF' (unlock) the PRNDL and several indicators will be functional but all gauges will not function. On transition from "OFF" (unlock) to run, the cluster will perform a check of all micro-controlled indicators, the odometer and the PRNDL for approx. 2 seconds. Other bulb checks with longer bulb check duration will be performed based on bus messages from other modules. If the cluster receives no PCI bus messages for (20) seconds after the transition to "run", the cluster will display "no bus" in the odometer.
A self test can be initiated by holding down the odometer reset button and switching the ignition from "lock" to "OFF" (unlock). This test will activate the gauges, turn ON the indicator lights along with the odometer and PRNDL segments.
MEMORY SYSTEM
The memory system consists of power left front seat, power mirrors and radio presets. The memory heated seat/mirror module (MHSMM) also includes the heated seat function. The module is located under the left front seat and receives input from: left manual 8-way seat switch, left seat position sensors, memory switch, both heated seat switches, both heated seat negative temperature coefficients (NTC's) thermistors), PCI bus circuits, and the power mirror sensors. The module uses these in- puts to perform the following functions: position the drivers memory seat, both exterior mirrors, actuate the drivers and passenger heated seat heater and send the memory location over the PCI bus.
When a memory button is pressed (either # 1 or # 2) on the memory switch the MHSMM sends a message to the BCM which in turn sends a recall message to the MHSMM and the PCI radio. They will in turn position the drivers seat and both mirrors along with setting the radio presets. If the drivers seat or either exterior mirrors are inoperative from their own respected switches, use the service information and schematic to diagnose the problem. This addresses the memory problems only and it is assumed there is not a basic component failure.
Power Seat
The memory power seat provides the driver with 2 position settings for the left seat. Each power seat motor is connected to the MHSMM with two circuits. Each circuit is switched between battery and ground. By alternating the circuits the MHSMM controls the movement of the motors based on input from the power seat switch or through memory recall.
Each motor contains a potentiometer to monitor the seat position. To monitor the position of the motor, the MHSMM sends out a 5-volt reference on the sensor supply circuit. The sensor is grounded back to the module on a common ground circuit. Based on the position of the sensor, the MHSMM monitors the voltage change through the sensor on a separate signal circuit.
The MHSMM stores the input value of each of the four seat potentiometers in memory when the system is requested. The driver can initiate memory recall, using either the seat mounted memory switch or the RKE transmitter. When initiated, the MHSMM adjusts the four seat motors to match the memorized seat position data.
For safety, the memory seat recall is disabled by the MHSMM when the vehicle is out of park position. Any obstruction to seat movement over a 2 second delay will cause the seat to stop moving in which case a stalled motor would be detected by the MHSMM which would then flag a trouble code and the corresponding seat output would be deactivated. However, if the object obstructing the seat is removed, the seat will function normally again.
Memory Seat Glide
The intent of this feature is to allow for easier entry and exit to the vehicle by moving the seat rearward a short distance when the operator turns the ignition OFF. The seat returns to its original position when the operator returns and turns ON the ignition or extends the seat belt. If any seat movement is initiated, whether manual or by memory recall, after the ignition has been turned OFF, that will cancel any ensuing glide to enter movement until the next ignition cycle.
This feature can be enabled/disabled by the owner by holding the memory set button and simultaneously pressing the horizontal rearward switch. To reinstate the feature, repeat the process. This can also be done using the DRB which will also inform as to which state it is in.
Guard Bands
The module provides guard bands which prevent the seat track from hitting the hard limits of the given seat axis during manual power seat operation. The guard band values for each hard limit are stored in EEPROM. The guard band can be bypassed by running the seat to the end of its travel and then releasing the switch and pressing it again. The seat will move a short distance further. Once the seat is past the guard band it can be stored in memory, but if recall is initiated the seat will move to the guard bands and no further.
Memory Mirrors
Each outside mirror has a vertical and a horizontal position sensor. The MHSMM provides a 5-volt reference to each position sensor. The sensors share a common ground circuit. The MHSMM monitors the position of the mirrors by measuring the voltage of each signal. When a memory position is set, the MHSMM monitors and stores the position of the outside mirrors. The MHSMM adjusts the mirrors to the appropriate positions when a memory recall message is received from the RKE or is requested from the memory switch.
The power mirror switch during non-memory operation operates both mirrors independently of the MHSMM.
Heated Seats
The controls for the heated seats are located on the side of each seat. The system offers two seat temperature settings of approximately 98.6 F (LO) and approximately 107.6 F (HI).
As the temperature in the seat rises, the Negative Temperature Coefficient (NTC) resistance decreases and the voltage reading detected by the MHSMM increases. The seat heater output is deactivated once the voltage reading reaches it's upper threshold for either setting, high or low.
As the temperature decreases, the voltage reading decreases until the lower threshold is reached for either setting high or low. At this point the seat heat output is activated once again and this cycle repeats itself as long as the seat heat request is ON. The thresholds for low and high settings are preprogrammed into the MHSMM memory.
The heated seat switch contain resistors pulled up to ignition which are processed by the MHSMM as voltage readings indicating desired heat setting high or low.
OVERHEAD CONSOLE
Overhead Travel Information System (OTIS)/Homelink
The Overhead Travel Information System (OTIS) gives the driver information that supplements the primary gauge instrumentation. OTIS displays this information on a Vacuum Fluorescent Display (VFD). The OTIS module has four switch inputs. The buttons for these switches are integral to the OTIS housing. There are two buttons on each side of the OTIS. The buttons are labeled US/M, C/T; STEP and RESET. The driver selects and resets display functions through the use of these four buttons. The OTIS will display these functions:
Compass/Temperature
AVE ECO Average Fuel Economy
ECO Instantaneous Fuel Economy
DTE Distance to Empty
ET Elapsed Time
ODO Trip Odometer
If the vehicle is equipped with the optional Homelink feature, the OTIS will have three buttons located in the center of the OTIS module. The OTIS module receives all of its information over the PCI bus except compass, which is internal to the OTIS module. The OTIS powers up when it recognizes vehicle voltage on the ignition input circuit. OTIS blanks the display, then illuminates all segments of the VFD. It then blanks the display again. During this time, the OTIS sends and receives information over the PCI bus to determine what to display after the two-second initialization. The OTIS displays dashes -- - -) for any of the screens for which it did not receive bus messages during the two-second initialization. These dashes will be replaced by valid information if and when it is received from the bus.
Setting The Compass
The compass in the OTIS module is self-calibrating and requires no manual adjustment. If calibration is required, the word CAL will be displayed to indicate that the compass is in the fast calibrating mode. "CAL" will turn OFF after the calibration is completed, only if the OTIS/HOMELINK System is not located within a high strength magnetic field.
Setting The Compass Variance
Variance is the difference between north and geographic north. To determine the variance for the area you are in, refer to the zone map below and follow the instructions provided. The number shown for your area is the variance number for your area
1. With ignition ON, use the C/T button to select the Compass/Temperature display.
2. Press and hold the RESET button for 5 seconds (but less than 10 seconds). OTIS displays the last variance zone and the word VAR. All other display segments are OFF.
3. Use the STEP button to select the proper variance zone number (1-15). Each variance zone represents a 4-degree shift in magnetic variation from central zone 8, which has no variation from true north.
4. After selecting the proper variance zone number, press the RESET switch. The new variance zone is then set and the OTIS will resume normal operation.