Part 2 of 3
DOOR AJAR SYSTEMThe door/deck ajar illuminated warning is accomplished by the words "DOOR" and "DECK" displayed on the odometer. The "DOOR" and "DECK" bulb check is performed at ignition ON and consists of an odometer display segment test. The door ajar is controlled by a MIC message from the BCM. The "DECK" ajar message is controlled by the MIC that is hardwired directly to the decklid ajar switch. The decklid ajar is also wired to the BCM. The hood ajar switch is wired to the BCM for use in the vehicle theft alarm system and does not have a warning lamp.
EXTERIOR LIGHTING CONTROL
The headlamps and park lamps are controlled by external relays which are controlled by the body control module. The headlamp relays are located in the power distribution center and the parklamp relay is located in the micro relay center behind the glove box. When the park lamp switch is turned ON (signals as a ground) the BCM then grounds the park lamp relay to provide power to the park, tail and marker lamps. The park lamp power feed, which is controlled by the BCM, also provides back-up power to the BCM. In the event that the ignition is turned OFF with the park lamps still ON, the BCM will function normally (as if the IOD had been reconnected) until the park lamps are turned OFF. When the headlamp switch is turned ON, (signals as a B+ feed) the BCM grounds low beam and high beam headlamp relay coils to turn ON the headlamps. However, the high beams will not turn ON until the dimmer switch is activated.
Headlamp Time Delay
The headlamp delay feature keeps the headlamps ON for 60 seconds, giving the driver and passenger security when exiting the vehicle. It is activated by sequentially turning OFF the ignition, and then turning OFF the headlamps. The headlamps must be turned OFF within 45 seconds of the ignition transition to OFF, to activate the headlamp delay. Once the headlamp delay has started the headlamps will remain ON for 60 seconds or until the park lamps (or headlamps) are cycled ON/OFF or the ignition is turned ON.
Battery Protection
If the park lamp or headlamp switch remains ON for more than 3 minutes while the ignition is OFF, the headlamps and park lamps will be turned OFF by the BCM and the input causing the lamps to be ON will be ignored until the condition is corrected. Once the 3 minute timeout has elapsed the BCM will enter sleep mode. This feature provides protection to avoid running the battery down in the event the customer fails to turn the lamps OFF.
INSTRUMENT CLUSTER (MIC)
The Prowler utilizes a 'smart' instrument cluster. The tachometer and the voltmeter gauges are hard-wired and are not part of the instrument cluster self test routine which will be explained later. They cannot be actuated. As mentioned previously, the tach is hardwired directly to the PCM, the illumination circuit, however, is part of the instrument panel lighting circuit. The voltmeter is hardwired to the B (+) circuit through the ignition switch.
The cluster positions its gauges based on a message formulated by the BCM for gauge position. All the sensors that are responsible for a gauge message are hardwired to the BCM. The BCM then builds the message and sends it over the CCD bus where the cluster will receive the message, decode it, and position all the gauge pointers at their proper positions.
The cluster also contains hardwired and CCD bus controlled warning lamps. A hardwired lamp is usually supplied B (+) by the cluster and ground by the circuit that it monitors. Any circuit that has a lamp that is CCD bus controlled will be an input to the BCM, except the Airbag Lamp which receives it's CCD messages from the Airbag Control Module (ACM). If no messages are received from the ACM for 5 seconds the Airbag lamp will be turned ON.
There is an onboard self-test that can be actuated standalone or with the DRBIII(R). During the self-test, the cluster will position all the gauges at predetermined calibration points, the CCD controlled lamps will be illuminated, as well as the segments of the LCD odometer. This allows verification of gauge operation, CCD operation, as well as a visual check of all the individual segments in the LCD odometer.
INTERIOR LIGHTING
Courtesy Lamp Control
The interior courtesy lamps located in the right and left foot well area, the rear view mirror and the ignition switch halo lamp are hardwired together and are controlled by the BCM. They can be activated by the dome lamp switch, by opening a door or by the RKE when it activates the BCM 30 second illuminated entry timer. The interior lamps will then fade to OFF over a 5 second period.
Reading Lamps
The reading lamps and control switches are mounted on the rear view mirror.
Interior Lamp Battery Protect Feature (Load Shedding)
To protect the battery from excessive current draw, the courtesy, halo, reading and glove box lamps are shut OFF after 15 minutes if they have been left ON or a door has been left ajar after the ignition key is removed from the ignition. This is accomplished by the BCM which removes ground from these lamps.
Instrument Panel Dimming
I/P dimming is accomplished using the body control module. The panel dimming level switch is read by the body control module and converted to a value that is sent over the CCD bus.
I/P Dimmer/dome Lamp Switch
This switch is part of the headlamp switch. It is used to adjust the intensity of the instrument panel lighting. Instrument panel dome lamps can be requested by rotating the I/P illumination switch fully counterclockwise.
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 or by opening any door. Upon exiting the vehicle, if the lock button is pressed with a door open, illuminated entry will cancel when the door closes. If the vehicle is secure, and a remote keyless entry lock message is received, illuminated entry will cancel. If the doors are closed and the ignition switch is turned ON, the illuminated entry also cancels.
LOW TIRE PRESSURE WARNING SYSTEM (LTPW)
This system monitors tire pressure and provides warning via a low tire warning lamp and an audible tone(s) when a tire's pressure has fallen below a predefined threshold. There are two thresholds, they are "Tire Pressure Low" and "Tire Pressure Critical". The system only operates when the vehicle is moving above approximately 33 km/h (20 mph). Above this speed, the low tire pressure warning system will continuously monitor the air pressure in all four tires. The low tire pressure warning system will alert the driver in the event the air pressure falls below a threshold in one or more of the tires.
The LTPW System consists of:
- Low Tire Pressure Warning Module
- 4 Tire Pressure Sensor/Transmitters
- Body Control Module (BCM)
- Low Tire Pressure Warning Indicator
The system operates by monitoring a radio frequency (RF) transmission from Tire Pressure Sensor/Transmitters located in each wheel, and integrated with the valve stem. The transmitter is powered by a battery located inside the assembly. To extend the life of the battery, the transmitter does not send a signal to the module at vehicle speeds below approximately 33 km/h (20 mph). When the vehicle attains a speed of approximately 33 km/h (20 mph), the centrifugal force of the rotating wheel closes a roll switch (inside the transmitter) that powers up the circuitry.
Each transmitter has a unique identity (ID) code. The ID code allows the module to indicate to the driver, through the Low Tire Warning Indicator, that one of the tires has lost air pressure. The DRBIII(R) can be used to tell which tire pressure sensor/transmitter has failed or sensed a low tire pressure based on its ID code.
Verification that the LTPW system is operational must be performed during a road test, since the system is only operational when the vehicle is moving more than 33 km/h (20 mph). The DRBIII(R) must not be connected during the road test. The DRBIII(R) can be used following the road test to check whether or not signals were received by the LTPW module.
Low Tire Pressure Warning Module
The LTPW module has a microprocessor controller that can monitor the transmissions from the transmitters at all times with the ignition ON. The LTPW module will store the last 32 transmissions from the tire pressure sensor/transmitters, however, they cannot be observed as they occur with the DRBIII(R). There are three important values included in these transmissions. They are listed as: why the transmission was sent, from which sensor it came from (LF, RF, RR, LR), and tire pressure. There are four reasons why the tire pressure sensor/transmitter will send information to the LTPW module they are listed below:
Supervisory - This is the normal mode, the transmitter will start to transmit information to the LTPW module at approximately 33 km/h (20 mph) and continue at a rate of approximately one transmission per minute.
6.9 kPa (1 psi) Change - If the pressure reading changes by more than 6.9 kPa (1 psi) between the normal sampling period of 30 seconds, the transmitter will send this change information to the LTPW module within approximately 30 seconds.
Wake - This is the very first message that the tire pressure sensor/transmitter sends to the LTPW module. This wake mode will only occur after the vehicle has reached the start to operate speed of approximately 33 km/h (20 mph).
Magnet - When a magnet is placed next to the transmitter it closes a reed switch inside and forces the transmitter to send a signal to the LTPW module. Placing a magnet next to the transmitter will normally be done for programming purposes when the LTPW module or the tire pressure sensor/transmitter is being replaced.
The module compares the transmitted tire pressure to the two pressure thresholds, low and critical. If the module determines that the tire pressure transmitted is below the low or critical pressure, the module will signal the "Low Tire" Pressure Warning Indicator to come ON.
The module performs diagnostic routines, stores diagnostic trouble codes and provides the appropriate Indicator status to the BCM. When the module determines that there is a fault, the low tire pressure signal circuit will be pulled low (grounded) and the BCM will turn ON the "Low Tire" lamp.
The LTPW module also stores its own ID number, each of the four transmitter ID numbers, module version and date of manufacture.
Tire Pressure Sensor/Transmitter
The system has four individual Tire Pressure Sensor/Transmitters, one mounted in each wheel. The valve stem is integral with the pressure sensor/transmitter. Each tire pressure sensor/transmitter serves three functions:
1. It is used as a valve stem to inflate and deflate the tire.
2. It periodically measures tire pressure. (Approximately every 30 seconds).
3. It transmits the tire pressure value to the LTPW Module in the vehicle. (Approximately every 60 seconds or 30 seconds or more if the tire pressure changes by 6.9 kPa (1 psi) between transmissions when the wheel is rotating above 33km/h (20 mph)).
The Tire Pressure Sensor/Transmitter unit consists of:
- Three volt battery
- Pressure sensor
- Roll switch (speed activated)
- Reed switch (magnet activated)
- Radio Frequency (RF) transmitter.
CAUTION: INFLATABLE TIRE SEALANTS FOR FIXING A SLOW LEAK OR FLAT TIRE SHOULD BE AVOIDED AS THE SEALANT WILL CLOG THE PRESSURE SENSING HOLE IN THE TRANSMITTER.
Battery
The three volt Lithium battery is used to power up the Integrated Circuit (IC) board in the Tire Pressure/Sensor Transmitter unit. The battery is only used above 33 km/h (20 mph) to improve its useful service life. The transmitters are capable of notifying the LTPW module when a battery is low. Upon receiving a low battery message, the LTPW module will track the status of the battery for 3 consecutive ignition cycles. (An ignition cycle is defined as: ignition ON, and left ON for at least 15 minutes, and vehicle speed above approximately 33 km/h (20 mph) long enough for the LTPW module to receive a transmission from each transmitter.) If the battery is still low after 3 consecutive ignition cycles, the LTPW Module will set a Diagnostic Trouble Code (DTC). The battery is a non-serviceable part and must be replaced with a complete Tire Pressure Sensor/Transmitter unit. The new tire pressure sensor/transmitter must be programmed using the DRBIII(R).
NOTE: TIRE PRESSURE SENSOR/TRANSMITTER REPLACEMENT INVOLVES REMOVAL OF THE TIRE FROM THE WHEEL.
Roll Switch
There is an integral roll switch within the Tire Pressure/Sensor Transmitter that must be closed before the transmitter is powered up. This roll switch is open when the vehicle is stopped or below approximately 33 km/h (20 mph). When the vehicle is moving above 33 km/h (20 mph) centrifugal force will close the roll switch, powering up the Tire Pressure Sensor/Transmitter unit.
NOTE: THE TRANSMITTER TAKES ABOUT 2 MINUTES TO FALL ASLEEP AFTER THE ROLL SWITCH OPENS.
Integrated Circuit
The Integrated Circuit (IC) will sample the tire pressure once every 30 - 34 seconds if the vehicle is moving above 33 km/h (20 mph). This IC also contains the tire pressure sensor/transmitter ID code.
Transmitter
The measured tire pressure value is transmitted when the vehicle speed is above approximately 33 km/h (20 mph), every 60 - 68 seconds or if the pressure drops 6.9 kPa (1 psi) or more between sampling periods. It is important to note that not all the tire pressure sensor/transmitters will start to transmit at the same time. Due to manufacturing tolerances some transmitters may start to operate with speeds as low as 16 km/h (10 mph).
The LTPW module continuously monitors and records the last 32 transmissions that it receives. When the LTPW module notices that one of the Tire Pressure Sensor/Transmitters has not sent its information within the last 32 transmission windows, it will set a Diagnostic Trouble Code (DTC) and turn the "Low Tire" Pressure Warning Indicator ON steady. If the transmitter begins transmitting again, the module will shut off the "Low Tire" Pressure Warning Indicator, however, the transmitter ID and number of occurrences are stored. This data is in the LTPW module memory and can be erased using the DRBIII(R). If this type of failure occurred, the BCM DTC will have to be cleared as well.
Reed Switch
A magnet is used to close the reed switch. The only time that the reed switch is used is when the LTPW module is programmed. When a magnet is placed over the end of the valve stem, it will close the reed switch. With the reed switch closed the transmitter will send its ID and tire pressure to the module. The ID and tire pressure can be read using the DRBIII(R).
Low Tire Pressure Warning Indicator and Warning Tone
The "Low Tire" Pressure Warning Indicator is located in the instrument cluster and is displayed as "Low Tire". The indicator is used to inform the driver that one or more of the tires have low air pressure. The "Low Tire" indicator is controlled by the LTPW module indirectly through the Body Control Module (BCM). The BCM controls the "Low Tire" indicator by communicating with the instrument cluster via the CCD Bus. The instrument cluster controls the "Low Tire" indicator by directly grounding the indicator. When the ignition is turned ON, the LTPW module grounds the Low Tire Pressure Signal circuit for 2 seconds. The BCM will then illuminate the "Low Tire" indicator for 2 seconds signifying that the system is operational. If the BCM does not sense that the LTPW module has provided a ground path after initial ignition ON, or the LTPW module has set a DTC and is keeping the Low Tire Pressure Warning Signal Circuit grounded, the BCM will set the Tire Pressure Input Circuit Fault DTC. The BCM will turn the "Low Tire" Pressure Warning Indicator ON and it will stay ON, signifying a problem with the LTPW system.
When the LTPW module senses that pressure is below one of two calibrated thresholds, Low pressure or Critical pressure the LTPW module will indirectly operate the "Low Tire" Pressure Warning indicator and the chime tone through the BCM.
If the tire pressure is low, the low tire pressure warning indicator signal circuit will be pulsed to ground by the LTPW module for two seconds ON and then two seconds OFF. The BCM will then illuminate the "Low Tire" Pressure Warning indicator at the same rate and operate the chime tone steadily with no pulsing.
If the tire pressure is critical, the low tire pressure warning indicator signal circuit will be pulsed to ground by the LTPW module for one second ON then one second OFF. The BCM will then illuminate the "Low Tire" indicator and sound the chime tone at the rate of one second OFF and one second ON.
The module will continue to pulse to ground the low tire pressure warning indicator signal circuit until the ignition is turned OFF, or the tire pressure transmitter(s) transmits a pressure above the calibrated threshold.
NOTE: A LOW TIRE PRESSURE CONDITION DOES NOT SET A DTC. THE DRBIII(R) CAN BE USED TO VIEW THE LAST 32 TRANSMISSIONS IN THE MODULE'S MEMORY AND TO CONFIRM WHICH TIRE WAS REPORTING THE LOW PRESSURE CONDITION.
If more than one condition is set at the same time, the LTPW module will prioritize how the "Low Tire" lamp will be illuminated. The priority rankings are listed below.
Critical Pressure Lamp flashes at one second ON and one second OFF
Low Pressure Lamp flashes at two seconds ON and two seconds OFF
LTPW Module Failure (DTC) Lamp ON steady
Tire Pressure Sensor/Transmitter (DTC) Lamp ON steady
Less than four transmitter IDs learned Lamp ON steady
Critical tire pressure is zero Lamp ON steady
Normal tire pressure No lamp
No faults No lamp
Low Tire Pressure Warning Module Modes
System Initialization
When the ignition is turned to the "run" position, the LTPW module performs a complete self-check of all electrical components in the module.
Operational Mode
After the vehicle reaches a speed of approximately 33 km/h (20 mph), the module will perform a dynamic check of the tire pressure transmitters. During the dynamic check, the vehicle speed may fall below 33 km/h (20 mph) but not for longer than one minute. The LTPW module will confirm if the Radio Frequency (RF) transmissions from each tire pressure transmitters have been received.
If any component exhibits a trouble condition during the initialization or dynamic check, the LTPW module will set a DTC and illuminate the "Low Tire" warning indicator. A fault can also occur if the LTPW module (after initialization) does not receive any transmissions from the transmitter/sensor for six consecutive ignition cycles.
Diagnostic Mode
Diagnostic mode is considered to be any time that the DRBIII(R) is hooked up to the DLC and is communicating with the LTPW module. In diagnostic mode, the LTPW module does not monitor or accept the tire pressure sensor/transmitter signal.
This means that you cannot read the tire pressure sensor/transmitter transmission information while driving the vehicle with the DRBIII(R) hooked up.
Program Mode
The Program Mode enables the LTPW module to record each wheel transmitter ID in the following order (LF, RF, RR, LR) in memory. The module must learn each of the four tire pressure sensor/ transmitters' identifications (ID). This transmitter ID "learning" is used so that if any other signals are being received by the LTPW module at this frequency, it won't be misinterpreted.
Programming is initially done at the assembly plant. If a LTPW module fails or one or more tire pressure sensor/ transmitter(s) fails, after replacement of the faulty component, the LTPW module's must be reprogrammed to learn the transmitter ID.
The DRBIII(R) can place the module in Program Mode. It is possible to reprogram only one tire pressure sensor/transmitter. To program a module place a magnet (special tool 8192) over the end of the LF wheel valve stem for approximately six seconds. The magnet will energize and close a reed switch. With the reed switch closed, the transmitter will transmit the identification (ID) and tire pressure to the module. After the module has learned that particular tire pressure sensor/transmitter ID, the magnet should be moved to each of the other wheels as directed by the DRBIII(R). Hold the magnet at each wheel for six seconds before moving onto the next wheel. Exit the Program Mode. The module will store the locations of each transmitter ID. Using the DRBIII(R), verify that the module programming is complete by looking at the tire pressure sensor/transmitter ID's and pressure values.