
3.5 COMMUNICATION
The Programmable Communication Interface or
PCI Bus is a single wire multiplexed network capa-
ble of supporting binary encoded messages shared
between multiple modules. The PCI bus circuit is
identified as D25 and is white with a violet tracer.
Additional tracer colors may be added to the violet
in 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 ªHubº 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 RG:
²Body Control Module
²Front Control Module
²Occupant Restraint Controller
²Left Side Impact Airbag Control Module
²Right Side Impact Airbag Control Module
²Controller Antilock Brake
²Powertrain Control Module
²Engine Control Module - Diesel Only
²Radio
²CD Changer
²Transmission Control Module
²Automatic Temperature Control Module
²A/C Heater Control Module (MTC)
²Sentry Key Immobilizer Module
²RKE/Thatcham Alarm Module
²Memory Seat/Mirror Module
²Overhead Console
²Mechanical Instrument Cluster
²Left Sliding Door Control Module
²Right Sliding Door Control Module
²Power Liftgate Module
Each module provides its own bias and termina-
tion 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 witha conventional voltmeter. The preferred method is
to use the DRBIIItlab scope. The 12v 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 following figure for some typical dis-
plays.
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 in-
clude 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:
²All gauges on the MIC stay at zero
²All telltales on MIC illuminate
²MIC backlighting at full intensity
²Dashed lines in the overhead console ambient
temperature display
²No response received from any module on the PCI
bus (except the PCM)
²No start (if equipped with Sentry Key Immobi-
lizer)
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 DRBIIIt.
Diagnosis starts with symptom identification. If a
complete PCI Bus Communication Failure is sus-
pected, begin by identifying which modules the
vehicle is equipped with and then attempt to get a
response from the modules with the DRBIIIt.Ifany
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 DRBIIItmay display ªBUS +/- SIG-
NAL OPENº or ªNO RESPONSEº 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 DRBIIItand 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.
11
GENERAL INFORMATION

TEST ACTION APPLICABILITY
3WARNING: DO NOT OPERATE THE DCHA IN AN ENCLOSED AREA SUCH
AS A GARAGE THAT DOES NOT HAVE EXHAUST VENTILATION FACILI-
TIES. ALWAYS VENT THE DCHA's EXHAUST WHEN OPERATING THE
DCHA. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN
PERSONAL INJURY OR DEATH.
WARNING: ALLOW THE DCHA ASSEMBLY TO COOL BEFORE PERFORM-
ING A COMPONENT INSPECTION/REPAIR/REPLACEMENT. FAILURE TO
FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY.
Turn the ignition off.
Inspect the DCHA fuel line exterior for restrictions, leakage, and damage.
Verify that the DCHA fuel line is installed correctly.
NOTE: Waxed fuel can obstruct the fuel line and reduce flow. Check for the
appropriate winter grade fuel and replace as necessary.
Check for obstructions in the fuel line. Refer to Fuel Line, Cleaning in the Service
Information.
Is the DCHA fuel line Ok?All
Ye s®Go To 4
No®Repair the DCHA fuel line as necessary in accordance with the
Service Information.
Perform CABIN HEATER VERIFICATION TEST - VER 1.
4WARNING: DO NOT OPERATE THE DCHA IN AN ENCLOSED AREA SUCH
AS A GARAGE THAT DOES NOT HAVE EXHAUST VENTILATION FACILI-
TIES. ALWAYS VENT THE DCHA's EXHAUST WHEN OPERATING THE
DCHA. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN
PERSONAL INJURY OR DEATH.
WARNING: ALLOW THE DCHA ASSEMBLY TO COOL BEFORE PERFORM-
ING A COMPONENT INSPECTION/REPAIR/REPLACEMENT. FAILURE TO
FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY.
Turn the ignition off.
Disconnect the Dosing Pump rubber insulators from the splash shield.
Disconnect the fuel line from the fuel outlet side of the Dosing Pump.
Using a suitable length of fuel line, connect one end to the fuel outlet side of the
Dosing Pump and place the other end in a suitable container.
Turn the ignition on.
CAUTION: For the result of this test to be valid, actuate the Dosing Pump
Prime twice if the DCHA fuel supply line was drained and then not primed
prior to performing this test.
NOTE: Allow the Dosing Pump Prime to run the full 45 seconds.
With the DRBIIItin System Tests, select Dosing Pump Prime.
When the Dosing Pump Prime is complete, measure the amount of fuel in the
container.
Does the Dosing Pump output approx 14 ml (0.5 oz) of fuel in a single Dosing Pump
Prime activation?All
Ye s®Go To 5
No®Replace the Dosing Pump in accordance with the Service Infor-
mation.
Perform CABIN HEATER VERIFICATION TEST - VER 1.
302
CABIN HEATER
B1800 NO START ÐContinued

Symptom:
LEFT FRONT WHEEL SPEED SIGNAL FAILURE
When Monitored and Set Condition:
LEFT FRONT WHEEL SPEED SIGNAL FAILURE
When Monitored: Wheel speed comparison is checked at drive off or every 7 milliseconds
(ms). Sensor signal continuity is checked every 7 milliseconds. Wheel speed phase length
supervision is checked every 7 milliseconds.
Set Condition: If, during an ABS stop, the CAB commands any valve solenoid on for an
extended length of time, and does not see a corresponding wheel speed change, the
Diagnostic Trouble Code (DTC) is set. The DTC can also set if the signal is missing or
erratic.
POSSIBLE CAUSES
SENSOR OR TONE WHEEL CONCERN
DTC INTERMITTENT
LEFT FRONT WHEEL SPEED SENSOR INOPERATIVE
INTERMITTENT SIGNAL DTC
TEST ACTION APPLICABILITY
1 With the DRBIIIt, erase DTCs.
Turn the ignition off.
Start the engine.
Slowly accelerate as straight as possible from a stop to 24 km/h (15 mph).
Using the DRBIIIt, monitor the Left Front Wheel Speed Sensor while an assistant
drives the vehicle.
With the DRBIIIt, monitor all wheel speed sensors.
Is Left Front WSS Signal 0 km/h (0 mph) or differing from others by more than 5
km/h (3 mph)?All
Ye s®Go To 2
No®Go To 3
2 Inspect the Left Front Wheel Speed Sensor, Connector and Tone Wheel.
NOTE: Inspect components for damage and correct installation.
Are there any visible Sensor, Connector or Tone Wheel concerns?All
Ye s®Correct the sensor, connector or tone wheel concern as necessary.
The vehicle must be driven at 25 km/h (15 mph) to extinguish the
ABS indicator.
Perform ABS VERIFICATION TEST - VER 1.
No®Replace the Left Front Wheel Speed Sensor in accordance with
the Service Information. The vehicle must be driven at 25 km/h
(15 mph) to extinguish the ABS indicator.
Perform ABS VERIFICATION TEST - VER 1.
17
BRAKES (CAB)

Symptom:
LEFT REAR WHEEL SPEED SIGNAL FAILURE
When Monitored and Set Condition:
LEFT REAR WHEEL SPEED SIGNAL FAILURE
When Monitored: Wheel speed comparison is checked at drive off or every 7 milliseconds
(ms). Wheel speed circuit continuity is checked every 7 milliseconds. Wheel speed phase
length supervision is checked every 7 milliseconds.
Set Condition: If, during an ABS stop, the CAB commands any valve solenoid on for an
extended length of time, and does not see a corresponding wheel speed change, the
Diagnostic Trouble Code (DTC) is set. The DTC can also set if the signal is missing or
erratic.
POSSIBLE CAUSES
SENSOR OR TONE WHEEL CONCERN
DTC INTERMITTENT
LEFT REAR WHEEL SPEED SENSOR INOPERATIVE
INTERMITTENT SIGNAL DTC
TEST ACTION APPLICABILITY
1 With the DRBIIIt, erase DTCs.
Turn the ignition off.
Start the engine.
Slowly accelerate as straight as possible from a stop to 24 km/h (15 mph).
Using the DRBIIIt, monitor the Left Rear Wheel Speed Sensor while an assistant
drives the vehicle.
With the DRBIIIt, monitor all wheel speed sensors.
Is Left Rear WSS Signal 0 km/h (0 mph) or differing from others by more than 5 km/h
(3 mph)?All
Ye s®Go To 2
No®Go To 3
2 Inspect the Left Rear Wheel Speed Sensor, Connector and Tone Wheel.
NOTE: Inspect components for damage and correct installation.
Are there any visible Sensor, Connector or Tone Wheel concerns?All
Ye s®Correct the sensor, connector or tone wheel concern as necessary.
The vehicle must be driven at 25 km/h (15 mph) to extinguish the
ABS indicator.
Perform ABS VERIFICATION TEST - VER 1.
No®Replace the Left Rear Wheel Speed Sensor in accordance with the
Service Information. The vehicle must be driven at 25 km/h (15
mph) to extinguish the ABS indicator.
Perform ABS VERIFICATION TEST - VER 1.
19
BRAKES (CAB)

Symptom:
RIGHT FRONT WHEEL SPEED SIGNAL FAILURE
When Monitored and Set Condition:
RIGHT FRONT WHEEL SPEED SIGNAL FAILURE
When Monitored: Wheel speed comparison is checked at drive off or every 7 milliseconds
(ms). Wheel speed continuity is checked every 7 milliseconds. Wheel speed phase length
supervision is checked every 7 milliseconds.
Set Condition: If, during an ABS stop, the CAB commands any valve solenoid on for an
extended length of time, and does not see a corresponding wheel speed change, the
Diagnostic Trouble Code (DTC) is set. The DTC can also set if the signal is missing or
erratic.
POSSIBLE CAUSES
SENSOR OR TONE WHEEL CONCERN
DTC INTERMITTENT
RIGHT FRONT WHEEL SPEED SENSOR INOPERATIVE
CAB - WON'T RESPOND TO RIGHT FRONT WHEEL SPEED SENSOR SIGNAL
INTERMITTENT SIGNAL DTC
TEST ACTION APPLICABILITY
1 With the DRBIIIt, erase DTCs.
Turn the ignition off.
Start the engine.
Slowly accelerate as straight as possible from a stop to 24 km/h (15 mph).
Using the DRBIIIt, monitor the Right Front Wheel Speed Sensor while an assistant
drives the vehicle.
With the DRBIIIt, monitor all wheel speed sensors.
Is Right Front WSS Signal 0 km/h (0 mph) or differing from others by more than 5
km/h (3 mph)?All
Ye s®Go To 2
No®Go To 3
2 Inspect the Right Front Wheel Speed Sensor, Connector and Tone Wheel.
NOTE: Inspect components for damage and correct installation.
Are there any visible Sensor, Connector or Tone Wheel concerns?All
Ye s®Correct the sensor, connector or tone wheel concern as necessary.
The vehicle must be driven at 25 km/h (15 mph) to extinguish the
ABS indicator.
Perform ABS VERIFICATION TEST - VER 1.
No®Replace the Right Front Wheel Speed Sensor in accordance with
the Service Information. The vehicle must be driven at 25 km/h
(15 mph) to extinguish the ABS indicator.
Perform ABS VERIFICATION TEST - VER 1.
24
BRAKES (CAB)

Symptom:
RIGHT REAR WHEEL SPEED SIGNAL FAILURE
When Monitored and Set Condition:
RIGHT REAR WHEEL SPEED SIGNAL FAILURE
When Monitored: Wheel speed comparison is checked at drive off or every 7 milliseconds
(ms). Wheel speed circuit continuity is checked every 7 milliseconds. Wheel speed phase
length supervision is checked every 7 milliseconds.
Set Condition: If, during an ABS stop, the CAB commands any valve solenoid on for an
extended length of time, and does not see a corresponding wheel speed change, the
Diagnostic Trouble Code (DTC) is set. The DTC can also set if the signal is missing or
erratic.
POSSIBLE CAUSES
SENSOR OR TONE WHEEL CONCERN
DTC INTERMITTENT
RIGHT REAR WHEEL SPEED SENSOR INOPERATIVE
INTERMITTENT SIGNAL DTC
TEST ACTION APPLICABILITY
1 With the DRBIIIt, erase DTCs.
Turn the ignition off.
Start the engine.
Slowly accelerate as straight as possible from a stop to 24 km/h (15 mph).
Using the DRBIIIt, monitor the Right Rear Wheel Speed Sensor while an assistant
drives the vehicle.
With the DRBIIIt, monitor all wheel speed sensors.
Is Right Rear WSS Signal 0 km/h (0 mph) or differing from others by more than 5
km/h (3 mph)?All
Ye s®Go To 2
No®Go To 3
2 Inspect the Right Rear Wheel Speed Sensor, Connector and Tone Wheel.
NOTE: Inspect components for damage and correct installation.
Are there any visible Sensor, Connector or Tone Wheel concerns?All
Ye s®Correct the sensor, connector or tone wheel concern as necessary.
The vehicle must be driven at 25 km/h (15 mph) to extinguish the
ABS indicator.
Perform ABS VERIFICATION TEST - VER 1.
No®Replace the Left Rear Wheel Speed Sensor in accordance with the
Service Information. The vehicle must be driven at 25 km/h (15
mph) to extinguish the ABS indicator.
Perform ABS VERIFICATION TEST - VER 1.
26
BRAKES (CAB)

(3) Using a sharp knife (such as a razor), slit the
bushing lengthwise (Fig. 24) to allow its removal
from the lower control arm (Fig. 24).
(4) Remove the bushing from the lower control
arm.
DISASSEMBLY - LOWER CONTROL ARM
(REAR BUSHING - HYDRO)
(1) Remove the lower control arm from the front
suspension cradle. (Refer to 2 - SUSPENSION/
FRONT/LOWER CONTROL ARM - REMOVAL)
(2) Mount the lower control arm in a visewithout
using excessive clamping force.
(3) Install Remover, Special Tool 8460, on hydro-
bushing as shown (Fig. 25). Removal Pin, Special
Tool 8460±3, must extend though hole in center of
bushing rear.(4) Tighten forcing screw of Bridge (Special Tool
8460±1), removing bushing from lower control arm.INSPECTION - LOWER CONTROL ARM
Inspect lower control arm for signs of damage from
contact with the ground or road debris. If lower con-
trol arm shows any sign of damage, inspect lower
control arm for distortion. Do not attempt to repair
or straighten a broken or bent lower control arm. If
damaged, the lower control arm casting is serviced
only as a complete component.
Inspect both lower control arm isolator bushings
for severe deterioration, and replace as required.
Inspect the rear hydro-bushing for seepage. Both
Fig. 23 CRADLE CROSSMEMBER REINFORCEMENT
ATTACHMENT
1 - STEERING GEAR
2 - RIGHT LOWER CONTROL ARM
3 - LEFT LOWER CONTROL ARM
4 - CRADLE CROSSMEMBER REINFORCEMENT
5 - REAR CRADLE CROSSMEMBER ISOLATOR BUSHING
6 - STABILIZER BAR
7 - CRADLE CROSSMEMBER
Fig. 24 Slit Lower Control Arm Rear Bushing
1 - REAR BUSHING
2 - SLIT CUT IN BUSHING
3 - LOWER CONTROL ARM
Fig. 25 HYDRO-BUSHING REMOVAL
1 - REMOVAL PIN (8460-3)
2 - BRIDGE (8460-1)
3 - HYDRO-BUSHING
4 - LOWER CONTROL ARM
RSFRONT2-13
LOWER CONTROL ARM (Continued)

(7) Install the jounce bumper on the strut shaft
(Fig. 39). The jounce bumper is to be installed with
the small end pointing downward.
(8) Install the dust shield on the strut. Collapse
and stretch the dust shield down over the top of the
jounce bumper until the dust shield snaps into the
slot on the jounce bumper. The jounce bumper will be
at the top of the inner dust boot. Return the dust
shield to its fully extended length.
(9) Install the strut through the bottom of the coil
spring until the lower spring seat contacts the lower
end of the coil spring. The clevis bracket on the strut
should point straight outward away from the com-
pressor (to the 6 o'clock position). This position
should be within 5É of the lower end tip of the coil
spring (Fig. 50). If necessary, reposition the strut or
coil spring in the compressor so both of these line up
straight outward away from the compressor (to the 6
o'clock position). Install the clamp to hold the strut
and coil together.
(10) Install the strut mount over the strut shaft
and onto the top of the pivot bearing and upper seat
as shown (Fig. 45). Loosely install the retaining nut
on the strut shaft.
(11) Install Strut Nut Socket (on the end of a
torque wrench), Special Tool 6864, on the strut shaft
retaining nut (Fig. 46). Next, install a 10 mm socket
on the hex on the end of the strut shaft. While hold-
ing the strut shaft from turning, tighten the strut
shaft retaining nut to a torque of 100 N´m (75 ft.
lbs.).NOTE: Before releasing the tension the compressor
has on the spring, using the following figure as ref-
erence (Fig. 51), make sure the upper spring seat,
coil spring and strut clevis bracket are all lined up
properly (within 5É of one another).
(12) Slowly release the tension from the coil spring
by backing off the compressor drive fully. As the ten-
sion is relieved, make sure the upper mount, pivot
bearing and upper seat are align properly. Remove
the clamp from the lower end of the coil spring and
strut. Push back the spring compressor upper and
lower hooks, then remove the strut assembly from
the spring compressor.
(13) Install strut assembly on the vehicle. (Refer to
2 - SUSPENSION/FRONT/STRUT - INSTALLA-
TION)
INSTALLATION - STRUT ASSEMBLY
CAUTION: Front strut coil springs are side-oriented.
When installing a strut assembly, make sure the
strut being installed has the correct coil spring for
that side of the vehicle. Springs on the left side of
the vehicle have a left-hand wind top-to-bottom
while springs on the right side have a right-hand
wind top-to-bottom (Fig. 50). Do not interchange the
two sides.
Fig. 50 COIL SPRING POSITIONING
1 - FRONT OF VEHICLE
2 - END OF RIGHT COIL SPRING AT STRUT LOWER SEAT
3 - LOWER SEATS OF STRUTS
4 - STRUT CLEVIS BRACKETS
5 - END OF LEFT COIL SPRING AT STRUT LOWER SEAT
Fig. 51 COMPONENTS LINED UP
1 - IMAGINARY VERTICAL LINE
2 - CLEVIS BRACKET
3 - END OF COIL SPRING
4 - NOTCH IN UPPER SPRING SEAT
2 - 24 FRONTRS
STRUT (Continued)