Part 3B
POWER SUNROOFThe power sunroof in the 2001 Grand Cherokee is now controlled by the Body Control Module (BCM). After the ignition has been turned OFF, the power sunroof will remain operational for an additional 45 seconds. If the front doors are opened during this time, the BCM will remove power from the sunroof.
Diagnostic Junction Port:
COMMUNICATION
The Programmable Communication Interface or PCI Bus is a single wire multiplexed network capable of supporting binary encoded messages shared between multiple modules. The PCI bus circuit is identified as D25 and is yellow with a violet tracer. Additional tracer colors may be added to the violet m order to distinguish between different module connections. The modules are wired in parallel. Connections are made in the harness using splices.
One splice called the Diagnostic Junction Port, serves as the "Hub" of the bus. The Diagnostic Junction Port provides an access point to isolate most of the modules on the bus in order to assist in diagnosing the circuit. The following modules are used on the WJ:
- Body Control Module
- Door Modules (Driver & Passenger)
- Airbag Control Module
- Controller Antilock Brake
- Powertrain Control Module
- Radio
- CD Changer
- Transmission Control Module
- Automatic Zone Control Module
- Sentry Key Immobilizer Module
- Memory and/or Heated Seats Module
- Electronic Vehicle Information Center
- Mechanical Instrument Cluster
Each module provides its own bias and termination in order to transmit and receive messages. The bus voltage is at zero volts when no modules are transmitting and is pulled up to about seven and a half volts when modules are transmitting.
The bus messages are transmitted at a rate averaging 10800 bits per second. Since there is only voltage present when the modules transmit and the message length is only about 500 milliseconds, it is ineffective to try and measure the bus activity with a conventional voltmeter. The preferred method is to use DRB III lab scope. The 12 V square wave selection on the 20-volt scale provides a good view of the bus activity. Voltage on the bus should pulse between zero and about seven and a half volts. Refer to the figure for some typical displays.
The PCI Bus failure modes are broken down into two categories. Complete PCI Bus Communication Failure and individual module no response. Causes of complete PCI Bus Communication Failure include a short to ground or battery on the PCI circuit. Individual module no response can be caused by an open circuit at either the Diagnostic Junction Port or the module, or an open battery or ground circuit to the affected module.
Symptoms of a complete PCI Bus Communication Failure would include but are not limited to:
- All gauges on the MIC stay at zero
- All telltales on MIC illuminate
- MIC backlighting at full intensity
- Dashed lines in the EVIC ambient temperature display
- No response received from any module on the PCI bus
- No start (if equipped with Sentry Key Immobilizer)
Symptoms of Individual module failure could include any one or more of the above. The difference would be that at least one or more modules would respond to the DRB III.
Diagnosis starts with symptom identification. If complete PCI Bus Communication Failure is suspected, begin by identifying which modules the vehicle is equipped with and then attempt to get a response from the modules with the DRB III. If any modules are responding, the failure is not related to the total bus, but can be caused by one or more modules PCI circuit or power supply and ground circuits. The DRB III may display "BUS +A SIGNAL OPEN" or "NO RESPONSE" to indicate a communication problem. These same messages will be displayed if the vehicle is not equipped with that particular module. The CCD error message is a default message used by the DRB III and in no way indicates whether or not the PCI bus is operational. The message is only an indication that a module is either not responding or the vehicle is not equipped. Refer to the application table for a list of standard and optional modules and their respective Diagnostic Junction Port pin assignments.
VEHICLE THEFT SECURITY SYSTEM
The vehicle theft security system (VTSS) is part of the body control module, which monitors vehicle doors, liftgate, liftglass and the ignition for unauthorized operation. The alarm activates by sounding the horn, flashing the headlamps, hazard lamps, and the VTSS indicator lamp. The VTSS does not prevent engine operation, this is done with the sentry key immobilizer module. Passive arming occurs upon normal vehicle exit by removing the ignition key opening the driver door, locking the doors with the power lock, and closing the driver door or locking the doors with RKE. The indicator lamp on the dash will flash for 15 seconds, showing that arming is in progress. If no monitored systems are activated during this period, the system will arm and the indicator will flash at a slower rate. When something triggers the alarm, the system will signal the headlamps, park lamps, and horn for about 18 minutes.
For complaints about the Theft Alarm going OFF on it's own, use the DRB III and select "Theft Alarm", "VTSS" then "Monitor Display" and read the "Alarm Tripped By" status.
Tamper Alert - The VTSS tamper alert will sound the horn three times upon disarming to indicate a tamper condition has occurred.
Manual Override - The system will not arm if the doors are locked using the manual lock control or if the locks are actuated by an inside occupant after the doors are closed.
To verify the system, proceed as follows:
1. Open the driver's door.
2. Remove the ignition key (but keep it in hand).
3. Lock the doors with the power lock switch or the RKE.
4. Close the driver's door.
NOTE:
- AFTER THE DOORS ARE CLOSED, LOCKING THE DOORS WITH RKE WILL ALSO ARM THE SYSTEM.
- IF THE VTSS INDICATOR LAMP FLASHED, THE SYSTEM IS OPERATIONAL AND VERIFIED. IF NOT, THERE MAY BE A PROBLEM WITH THE SYSTEM.
Arming/Disarming - Active arming occurs when the remote keyless entry transmitter is used to lock the vehicle doors, whether the doors are open or closed. If one or more doors are open, the arming sequence is completed only after all doors are closed.
Passive disarming occurs upon normal vehicle entry (unlocking driver's door with the key). This disarming also will halt the alarm once it has been activated.
Active disarming occurs when the remote keyless entry transmitter is used to unlock the vehicle doors. This disarming also will halt the alarm once it has been activated.
System Self-Tests - NOTE: System self-tests can be entered only with the DRB III.
NOTE: A POWERTRAIN CONTROL MODULE FROM A VEHICLE EQUIPPED WITH A VEHICLE THEFT SECURITY SYSTEM CANNOT BE USED IN A VEHICLE THAT IS NOT EQUIPPED WITH A VEHICLE THEFT SECURITY SYSTEM. IF THE VTSS INDICATOR LAMP COMES ON AFTER IGNITION ON AND STAYS ON, THE PCI BUS COMMUNICATION WITH THE POWERTRAIN CONTROL MODULE POSSIBLY HAS BEEN LOST.
WINDSHIELD WIPER & WASHER
FRONT WIPER SYSTEM
System Description
The front wiper system consists of the following features: lo-hi-speed, mist wipers, intermittent wipers, and wipe after wash. The front wiper system is only active when the ignition is in the run/acc position.
The BCM controls the front wiper system with one low-going output to a relay. With this output the BCM determines the motor wipe rate. This rate is a function of the intermittent wiper switch position and vehicle speed. The BCM times the delay after the wipers have parked. If the driver goes from a longer to a shorter delay interval, a wipe is done immediately. The speed sensitive delay is set based on the current speed of the vehicle. If the vehicle crosses above the speed threshold of 10 MPH (16 kMH) while the intermittent wiper delay is occurring, a smaller delay can be used. If the vehicle crosses below the speed threshold a longer delay should not be used until the current delay is completed.
In the lo-hi and mist state, the BCM constantly outputs an active control signal for a delay of zero. The multifunction switch controls the wiper high/low relay wiper motor in the hi state. This is done with an additional output from the multifunction switch to a relay which selects the motor winding to be energized. The BCM does not distinguish between lo-hi-or mist positions. The mist position is a momentary input to the BCM which causes the wipers to operate at low speed as long as the mist input is present.
The BCM also monitors the front washer motor to perform wipe after wash. The BCM will perform 3 wipes after the wash input is released.
Since the front wiper system is an important safety feature, the BCM will support wiper operation in the event of a failed park input.
If BCM does not detect a change of state on the park input for 8 seconds with the wiper relay energized a Diagnostic Trouble Code will set in the BCM.
Once a failed park switch is detected, intermittent operation is disabled and the BCM will default to the low speed wiper state when the wiper switch is in the intermittent position. The wiper relay will be de-energized when the wiper mode switch is in the OFF position. For open and short states on the wiper mode switch, the wipers should default to OFF.
System Features
Speed Sensitive Intermittent Wipe Mode
There are 5 individual delay times with a minimum delay of 1/2 second to a maximum of 18 seconds. When the vehicle speed is under 10 mph (16 km/h), the delay time is doubled providing a range of 1 second to 36 seconds.
Mist Wipe
The wiper operates as long as the wiper switch is in the mist position.
Park after Ignition OFF
Because the wiper relays are powered from the battery the BCM can run the wipers to park after the ignition is turned OFF.
Wipe after Wash
When the driver presses the wash button and then releases it, the wiper will continue to run for 3 additional wipe cycles.
The wiper system utilizes the BCM to control the on/OFF relay for low wiper functions, intermittent wiper delay as the switch position changes, pulse wipe, wipe after wash mode, and wiper motor park functions. The BCM uses the vehicle speed input to double the usual delay time below 10 mph (16 km/h).
Front/Rear Wiper And Washer Switches (Right Multi-Function Switch Stalk)
The front windshield and rear liftglass wiper/washer switches are located on the wiper multi- function switch stalk which is secured to the right side of the multi-function switch mounting housing on the steering column.
A knob on the end of the wiper multifunction switch stalk is rotated to select the desired front wiper speed (HIGH or LOW) or one of the five intermittent front wiper positions. The wiper stalk is pulled toward the driver to activate the windshield washer system. Both the front wiper and front washer motors will operate continuously for as long as the stalk is held in the momentary FRONT WASH position.
Another rotary switch on the wiper multi- function switch stalk is rotated to select the desired rear wiper speed (ON or DELAY). The wiper stalk is pushed toward the instrument panel to activate the rear liftglass washer system. Both the rear wiper and rear washer motors will operate continuously for as long as the stalk is held in the momentary REAR WASH position.
If any part of the right multi-function switch stalk is faulty or damaged, the entire wiper multi- function switch assembly must be replaced.
Rear Wiper System Control Circuits:
REAR WIPER SYSTEM
Five circuits feed the rear wiper module. It has two high current circuits, battery (B+) and ground, that run the motor. The remaining three circuits are low current control circuits.
Two of these circuits come from the rear wiper switch on the right multi-function switch stalk. These circuits are referred to as the rear wiper motor control circuit and the rear wiper motor intermittent control circuit. When the rear wiper switch is in the OFF position, both of these circuits are open and the wiper module parks or remains parked. When the rear wiper switch is in the Intermittent position, the intermittent control circuit is switched to ignition voltage, the motor control circuit is open and the wiper is in the intermit- tent modes. When the rear wiper switch is in the ON position, the intermittent control circuit is open and the motor control circuit is switched to ignition voltage and the wiper is in continuous wipe mode.
The third control circuit is the AJAR circuit. This circuit is fed by the flip-up glass ajar switch. When the flip-up glass is closed the ajar switch is open and the rear wiper module functions normally. When the flip-up glass is open, the ajar switch is closed and the circuit provides ground to the module. This ground signal indicates to the rear wiper module that it should park if operating or not allow operation if parked.