
4.2.4 DRBIIITSAFETY INFORMATION
WARNING: EXCEEDING THE LIMITS OF THE
DRBIIITMULTIMETER IS DANGEROUS. IT
CAN EXPOSE YOU TO SERIOUS OR
POSSIBLE FATAL INJURY. CAREFULLY
READ AND UNDERSTAND THE CAUTIONS
AND THE SPECIFICATION LIMITS.
²Follow the vehicle manufacturer 's service speci-
fications at all times.
²Do not use the DRBIIItif it has been damaged.
²Do not use the test leads if the insulation is
damaged or if metal is exposed.
²To avoid electrical shock, do not touch the test
leads, tips, or the circuit being tested.
²Choose the proper range and function for the
measurement. Do not try voltage or current mea-
surements that may exceed the rated capacity.
²Do not exceed the limits shown in the table below:
FUNCTION INPUT LIMIT
Volts 0 - 500 peak volts AC
0 - 500 volts DC
Ohms (resistance)* 0 - 1.12 megaohms
Frequency Measured
Frequency Generated0-10kHz
Temperature -58 - +1100ÉF
-50 - +600ÉC
* Ohms cannot be measured if voltage is present.
Ohms can be measured only in a non-powered
circuit.
± Voltage between any terminal and ground
must not exceed 500v DC or 500v peak AC.
± Use caution when measuring voltage above
25v DC or 25v AC.
± Use the low current shunt to measure circuits
up to 10A. Use the high current clamp to
measure circuits exceeding 10A.
± When testing for the presence of voltage or
current, make sure the meter is functioning
correctly. Take a reading of a known voltage or
current before accepting a zero reading.
± When measuring current, connect the meter in
series with test load.
± When using the meter function, keep the
DRBIIItaway from spark plug or coil wires to
avoid measuring error from outside interfer-
ence.
4.3 WARNING
4.3.1 VEHICLE DAMAGE WARNINGS
Before disconnecting any control module, make
sure the ignition is ``off ''. Failure to do so could
damage the module.
When testing voltage or continuity at any control
module, use the terminal side (not the wire end) of
the connector. Do not probe a wire through the
insulation; this will damage it and eventually cause
it to fail because of corrosion.
Be careful when performing electrical tests so as
to prevent accidental shorting of terminals. Such
mistakes can damage fuses or components. Also, a
second code could be set, making diagnosis of the
original problem more difficult.
4.3.2 ROAD TESTING A COMPLAINT
VEHICLE
Some complaints will require a test drive as part
of the repair verification procedure. The purpose of
the test drive is to try to duplicate the diagnostic
code or symptom condition.
CAUTION: Before road testing a vehicle, be
sure that all components are reassembled.
During the test drive, do not try to read the
DRBIIITscreen while in motion. Do not hang
the DRBIIITfrom the rear view mirror or
operate it yourself. Have an assistant
available to operate the DRBIIIT.
4.4 DIAGNOSIS
1. Your diagnostic test procedure must begin with a
thorough visual inspection of the system in ques-
tion for damaged components or disconnected
connectors. For ABS, the brake lamps must be
operational prior to continuing.
2. Connect the DRBIIItto the data link connector
located under the dash. If the DRBIIItdoes not
power up, check the power and ground supplies
to the connector.
3. Select the system in question. Turn the ignition
on. If the DRBIIItdisplays ``No Responseº, refer
to Communication in the Body Diagnostic Pro-
cedures manual to diagnose the symptom.
4. Read and record all diagnostic trouble codes. If
any additional codes are present, proceed to the
appropriate test.
5. For ABS, if there are no diagnostic trouble codes
present, select ``Inputs/Outputs'' and read the
Brake Switch and Brake Lamp Switch inputs as
you press and release the brake pedal. If the
6
GENERAL INFORMATION

display does not match the state of the pedal,
perform the proper test. For a problem with the
ªABSº warning indicator, refer to the proper test.
6. If no other problems are found, it will be neces-
sary to road test the vehicle.THE DRBIIIt
MUST NOT BE CONNECTED TO THE
DATA LINK CONNECTOR WHEN ROAD
TESTING FOR PROPER ANTILOCK OP-
ERATION. THE SYSTEM IS DISABLED
WHILE IN DIAGNOSTIC MODE.Perform
several antilock stops from above 50 Km/h (30
mph) and then repeat steps 2, 3, and 4. If any
diagnostic trouble codes are present, proceed to
the appropriate test.
7. The following conditions should be considered
``NORMAL'' operation, and no repairs should be
attempted to correct them.
± Brake pedal feedback during an ABS stop
(clicking, vibrating)
± Clicking, groaning or buzzing at 12 Km/h (8
mph) (drive off self test)
± Groaning noise during an ABS stop
± Slight brake pedal drop and pop noise when
ignition is initially turned on
± Brake pedal ratcheting down at the end of an
ABS stop
8. If the complaint is ABS ``cycling'' at the end of a
stop at low speeds, it may be caused by a
marginal wheel speed sensor signal. The sensor
air gap, tone wheel condition, and/or brakes
hanging up are possible causes of this condition.
9. After a road test in which no problems were
found, refer to any Technical Service Bulletins
that may apply.
5.0 REQUIRED TOOLS AND
EQUIPMENT
DRBIIIt(diagnostic read-out box)
jumper wires
ohmmeter
voltmeter
test light
oscilloscope
6.0 GLOSSARY OF TERMS
ABSantilock brake system
ACalternating current
BCMbody control module
BSbrake switch
BLSbrake lamp switch
CABcontroller antilock brakeDCdirect current
DLCdata link connector
DRBIIItdiagnostic read-out box
DTCdiagnostic test code
EBDelectronic brake distribution
ECMelectronic control module
HCUhydraulic control unit
HZHertz
ICinstrument cluster
LFleft front
LRleft rear
PMpump motor
RFright front
RRright rear
SOLsolenoid
TCStraction control system
TCSStraction control system switch
VSSvehicle speed signal
WSSwheel speed sensor
7
GENERAL INFORMATION

TEST ACTION APPLICABILITY
3 Turn the ignition off.
Disconnect the CAB harness connector.
Inspect the CAB/CAB harness connector for damage.
Is there any broken, bent, pushed out, corroded or spread terminals?All
Ye s!Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
No!Go To 4
4 Turn the ignition off.
Turn the ignition on.
With the DRBIIItin Sensors, read the Relay Output voltage.
Start the engine.
With the DRBIIItin Sensors, read the Relay Output voltage.
Select the Relay Output voltage that was displayed on the DRBIIIt.All
Voltage below 9.4 volts.
Go To 5
Voltage above 17.4 volts.
Go To 7
Voltage between 9.4 and 17.4 volts.
Go To 8
5 Turn the ignition off.
Disconnect the CAB harness connector.
Start the engine.
Allow the engine to idle.
WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
Measure the voltage of the Fused Optional Equipment Relay Output circuit in the
CAB harness connector.
Raise the engine speed above 2,000 RPM's.
Measure the voltage of the Fused Optional Equipment Relay Output circuit in the
CAB harness connector.
Is the voltage less than 9.4 volts?All
Ye s!Repair the Fused Optional Equipment Relay Output circuit for an
open.
Perform ABS VERIFICATION TEST - VER 1.
No!Go To 6
61
BRAKES (CAB)
RELAY OUTPUT VOLTAGE ÐContinued

TEST ACTION APPLICABILITY
6 Turn the ignition off.
Disconnect the CAB harness connector.
Start the engine.
Allow the engine to idle.
WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
Measure the voltage of both Fused B(+) circuits in the CAB harness connector.
Raise the engine speed above 2,000 RPM's.
Measure the voltage of both Fused B(+) circuits in the CAB harness connector.
Is the voltage below 9.4 volts?All
Ye s!Repair the Fused B(+) circuit for an open.
Perform ABS VERIFICATION TEST - VER 1.
No!Go To 7
7 Turn the ignition off.
Disconnect the CAB harness connector.
Measure the voltage between the Fused B(+) circuit and both Ground circuits in the
CAB harness connector.
Is the voltage above 9.4 volts?All
Ye s!Repair any charging system related DTCs before continuing. If no
charging system or system voltage DTCs are present in any
module, replace the Controller Antilock Brake in accordance with
the Service Information.
Perform ABS VERIFICATION TEST - VER 1.
No!Repair the Ground circuit for an open.
Perform ABS VERIFICATION TEST - VER 1.
8 Turn the ignition off.
Visually inspect the related wiring harness.
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out, or corroded terminals.
Ensure the battery is fully charged.
Inspect the vehicle for aftermarket accessories that may exceed the Generator
System output.
Were any problems found?All
Ye s!Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
No!Test Complete.
62
BRAKES (CAB)
RELAY OUTPUT VOLTAGE ÐContinued

INSTRUMENT CLUSTER C2 - WHITECAV CIRCUIT FUNCTION
1- -
2- -
3 20RD/YL FUSED B(+)
4 20BR/WT BRAKE WEAR SENSOR SIGNAL
5- -
6 18BR GROUND
7 20GY/DG/RD LAMP DRIVER
8 20BL/WT FUSED HIGH BEAM SWITCH OUTPUT
9 20BL/RD/WT VEHICLE SPEED SENSOR OUTPUT
10 20BK FUSED IGNITION SWITCH OUTPUT (RUN-START)
11 20BL/BK KEY-IN IGNITION SWITCH SIGNAL
12 - -
13 20BK/WT LEFT TURN SIGNAL
14 20BR/YL BRAKE FLUID LEVEL INDICATOR SIGNAL
15 20BL GENERATOR FIELD DRIVER
16 20YL AIRBAG WARNING INDICATOR DRIVER
17 - -
18 20BL/VT D(+) RELAY NO. 1 CONTROL
18 20BL/VT D(+) RELAY NO. 1 CONTROL
STEERING ANGLE SENSORCAV CIRCUIT FUNCTION
1 20DG/WT CAN C BUS (-)
2- -
3 20DG CAN C BUS (+)
4- -
5 20BK/RD FUSED OPTIONAL EQUIPMENT RELAY OUTPUT
6 20BR GROUND
TCS SWITCH (ASR) - BLACKCAV CIRCUIT FUNCTION
1 16GY/DG/RD LAMP DRIVER
2- -
3 18BK/BL TCS SWITCH (ASR) SENSE
4- -
5- -
6- -
7 16BK/BL/DG FUSED IGNITION SWITCH OUTPUT
8- -
9- -
10 16BR GROUND
WHEEL SPEED SENSOR-LEFT FRONTCAV CIRCUIT FUNCTION
1 18BK LEFT FRONT WHEEL SPEED SENSOR (+)
2 18BR LEFT FRONT WHEEL SPEED SENSOR (-)
C
O
N
N
E
C
T
O
R
P
I
N
O
U
T
S
85
CONNECTOR PINOUTS

TABLE OF CONTENTS
1.0 INTRODUCTION.........................................................1
1.1SYSTEM COVERAGE...............................................1
1.2SIX-STEP TROUBLESHOOTING PROCEDURE..........................1
2.0 IDENTIFICATION OF SYSTEM.............................................1
3.0 SYSTEM DESCRIPTION AND FUNCTIONAL OPERATION......................1
3.1GENERAL DESCRIPTION............................................1
3.2FUNCTIONAL OPERATION...........................................1
3.2.1ECM ON-BOARD DIAGNOSTICS..............................1
3.2.2ECM OPERATING MODES...................................2
3.2.3MONITORED CIRCUITS......................................2
3.2.4SKREEM OVERVIEW........................................2
3.2.5SKREEM ON-BOARD DIAGNOSTICS...........................2
3.2.6SKREEM OPERATION.......................................3
3.3DIAGNOSTIC TROUBLE CODES......................................3
3.3.1HARD CODE...............................................3
3.3.2INTERMITTENT CODE.......................................3
3.3.3ECM DIAGNOSTIC TROUBLE CODES..........................3
3.3.4HANDLING NO TROUBLE CODE PROBLEMS...................8
3.4USING THE DRBIIIT.................................................8
3.4.1DRBIIITDOES NOT POWER UP...............................8
3.4.2DISPLAY IS NOT VISIBLE....................................8
4.0 DISCLAIMERS, SAFETY, WARNINGS.......................................8
4.1DISCLAIMERS......................................................8
4.2SAFETY...........................................................8
4.2.1TECHNICIAN SAFETY INFORMATION..........................8
4.2.2VEHICLE PREPARATION FOR TESTING........................9
4.2.3SERVICING SUB-ASSEMBLIES...............................9
4.2.4DRBIIITSAFETY INFORMATION...............................9
4.3WARNINGS AND CAUTIONS.........................................9
4.3.1ROAD TEST WARNINGS.....................................9
4.3.2VEHICLE DAMAGE CAUTIONS...............................9
5.0 REQUIRED TOOLS AND EQUIPMENT......................................9
6.0 GLOSSARY OF TERMS..................................................10
7.0 DIAGNOSTIC INFORMATION AND PROCEDURES...........................11
COMMUNICATION
*NO RESPONSE FROM ENGINE CONTROL MODULE........................12
*NO RESPONSE FROM SENTRY KEY REMOTE ENTRY MODULE..............14
DRIVEABILITY - DIESEL
P-1105 ATMOSPHERIC PRESSURE SENSOR PLAUSIBILITY WITH BOOST
PRESSURE SENSOR....................................................16
P1105-ATMOSPHERIC PRESSURE SENSOR SIGNAL VOLTAGE TOO HIGH......16
P1105-ATMOSPHERIC PRESSURE SENSOR SIGNAL VOLTAGE TOO LOW......16
P1617- ECM READ/WRITE ERROR........................................16
i

3.3.4 HANDLING NO TROUBLE CODE
PROBLEMS
After reading Section 3.0 (System Description
and Functional Operation), you should have a bet-
ter understanding of the theory and operation of the
on-board diagnostics and how this relates to the
diagnosis of a vehicle that may have a driveability-
related symptom or complaint. When there are no
trouble codes present, refer to the no trouble code
(*) tests.
3.4 USING THE DRBIIIT
Refer to the DRBIIItuser 's guide for instructions
and assistance with reading the DTCs, erasing the
DTCs, lab scope usage and other DRBIIItfunc-
tions.
3.4.1 DRBIIITDOES NOT POWER UP
If the LEDs do not light or no sound is emitted at
start up, check for loose cable connections or a bad
cable. Check the vehicle battery voltage at data link
connector cavity 16. A minimum of 11.0 volts is
required to adequately power the DRBIIIt. Check
for proper ground connection at data link connector
cavities 4 and 5.
If all connections are proper between the
DRBIIItand the vehicle or other devices, and the
vehicle battery is fully charged, an inoperative
DRBIIItmay be the result of a faulty cable or
vehicle wiring. For a blank screen, refer to the
appropriate diagnostic manual.
3.4.2 DISPLAY IS NOT VISIBLE
Low temperatures will affect the visibility of the
display. Adjust the contrast to compensate for this
condition.
4.0 DISCLAIMERS, SAFETY,
WARNINGS
4.1 DISCLAIMERS
All information, illustrations and specifications
contained in this manual are based on the latest
information available at the time of publication.
The right is reserved to make changes at any time
without notice.
4.2 SAFETY
4.2.1 TECHNICIAN SAFETY INFORMATION
WARNING: HIGH-PRESSURE FUEL LINES
DELIVER DIESEL FUEL UNDER EXTREME
PRESSURE FROM THE INJECTION PUMP TO
THE FUEL INJECTORS. THIS MAY BE AS
HIGH AS 23,200 PSI (1600 BAR). USE
EXTREME CAUTION WHEN INSPECTING
FOR HIGH-PRESSURE FUEL LEAKS. FUEL
UNDER THIS AMOUNT OF PRESSURE CAN
PENETRATE SKIN CAUSING PERSONAL
INJURY OR DEATH. INSPECT FOR
HIGH-PRESSURE FUEL LEAKS WITH A
SHEET OF CARDBOARD. WEAR SAFETY
GOGGLES AND ADEQUATE PROTECTIVE
CLOTHING WHEN SERVICING FUEL
SYSTEM.
WARNING: ENGINES PRODUCE CARBON
MONOXIDE THAT IS ODORLESS, CAUSES
SLOWER REACTION TIME AND CAN LEAD
TO SERIOUS INJURY. WHEN THE ENGINE IS
OPERATING, KEEP SERVICE AREA WELL
VENTILATED OR ATTACH THE VEHICLE
EXHAUST SYSTEM TO THE SHOP EXHAUST
REMOVAL SYSTEM.
Set the parking brake and block the wheels before
testing or repairing the vehicle. It is especially
important to block the wheels on front wheel drive
vehicles; the parking brake does not hold the drive
wheels.
When servicing a vehicle, always wear eye pro-
tection and remove any metal jewelry such as
watchbands or bracelets that might make electrical
contact.
When diagnosing powertrain system problems, it
is important to follow approved procedures where
applicable. These procedures can be found in the
8
GENERAL INFORMATION

service manual. Following these procedures is very
important to the safety of the individuals perform-
ing the diagnostic tests.
4.2.2 VEHICLE PREPARATION FOR
TESTING
Make sure the vehicle being tested has a fully
charged battery. If it does not, false diagnostic codes
or error messages may occur.
4.2.3 SERVICING SUB-ASSEMBLIES
Some components of the powertrain system are
intended to be serviced as an assembly only. At-
tempting to remove or repair certain system sub-
components may result in personal injury and/or
improper system operation. Only those components
with approved repair and installation procedures in
the service manual should be serviced.
4.2.4 DRBIIITSAFETY INFORMATION
WARNING: EXCEEDING THE LIMITS OF THE
DRBIIITMULTIMETER IS DANGEROUS. IT
CAN EXPOSE YOU TO SERIOUS OR
POSSIBLE FATAL INJURY. CAREFULLY
READ AND UNDERSTAND THE CAUTIONS
AND SPECIFICATION LIMITS.
Follow the vehicle manufacturer 's service specifi-
cations at all times.
± Do not use the DRBIIItif it has been dam-
aged.
± Do not use the test leads if the insulation is
damaged or if metal is exposed.
± To avoid electrical shock, do not touch the test
leads, tip or the circuit being tested.
± Choose the proper range and function for the
measurement. Do not try voltage or current
measurements that may exceed the rated ca-
pacity.
± Do not exceed the limits shown in the table
below:
FUNCTION INPUT LIMIT
Volts 0±500 peak volts AC
0±500 volts DC
Ohms (Resistance)* 0±1.12 megaohms
Frequency Measure
Frequency Generated0±10 kHz
Temperature ±58 ± +1100ÉF
±50 ± +600ÉC
* Ohms cannot be measured if voltage is present.
Ohms can be measured only on a non-powered
circuit.± Voltage between any terminal and ground
must not exceed 500v DC or 500v peak AC.
± Use caution when measuring voltage above
25v DC or 25v AC.
± The circuit being tested must be protected by a
10 amp fuse or circuit breaker.
± Use the low current shunt to measure circuits
up to 10 amps. Use the high current shunt to
measure circuits exceeding 10 amps.
± When testing for the presence of voltage or
current, make sure the meter is functioning
correctly. Take a reading of a known voltage or
current before accepting a zero reading.
± When measuring current, connect the meter in
series with the load.
± Disconnect the live test lead before disconnect-
ing the common test lead.
4.3 WARNINGS AND CAUTIONS
4.3.1 ROAD TEST WARNINGS
Some complaints will require a test drive as part
of the repair verification procedure. The purpose of
the test drive is to try to duplicate the diagnostic
code or symptom condition.
CAUTION: Before road testing a vehicle, be
sure that all components are reassembled.
During the test drive, do not hang the DRBIIIT
from the rear view mirror. Do not attempt to
read the DRBIIITwhile driving. Have an
assistant available to operate the DRBIIIT.
4.3.2 VEHICLE DAMAGE CAUTIONS
Before disconnecting any control module, make
sure the ignition is off. Failure to do so could
damage the module. When testing voltage or circuit
integrity at any control module, use the terminal
side (not the wire end) of the harness connector. Do
not probe through the insulation; this will damage
it and eventually cause it to fail because of corro-
sion.
Be careful when performing electrical test so as to
prevent accidental shorting of terminals. Such a
mistake can damage fuses or components. Also, a
second code could be set, making diagnosis of the
original problem more difficult.
5.0 REQUIRED TOOLS AND
EQUIPMENT
DRBIIIt(diagnostic read-out box) scan tool
vacuum gauge
ammeter
9
GENERAL INFORMATION