
ver: 2.14
date: 26 Jul93
file: key_iff.cc
date: Jul 26 1993
line: 548
err: 0x1
User-Requested COLD Boot
Press MORE to switch between this display
and the application screen.
Press F4 when done noting information.
3.9.1 DRBIIITDOES NOT POWER UP
(BLANK SCREEN)
If the LED's 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 (data link
16-way connector cavity 16). A minimum of 11 volts
is required to adequately power the DRBIIIt. Also
check for a good ground at DLC.
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 or a faulty cable or
vehicle wiring.
3.9.2 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 latestinformation 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: ENGINES PRODUCE CARBON
MONOXIDE THAT IS ODORLESS, CAUSES
SLOWER REACTION TIME, AND CAN LEAD
TO SERIOUS INJURY. WHEN THE ENGINE IS
OPERATING, KEEP SERVICE AREAS 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 front
drive wheels.
When servicing a vehicle, always wear eye pro-
tection, and remove any metal jewelry such as
watchbands or bracelets that might make an inad-
vertent electrical contact.
When diagnosing an antilock brake or adjustable
pedals system problem, it is important to follow
approved procedures where applicable. These pro-
cedures can be found in the service manual. Follow-
ing these procedures is very important to safety of
individuals performing 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 antilock brake and trac-
tion control are intended to be serviced in assembly
only. Attempting to remove or repair certain 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.
5
GENERAL INFORMATION

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

Symptom:
BRAKE FLUID LEVEL
POSSIBLE CAUSES
INTERMITTENT DTC
BRAKE FLUID LEVEL SWITCH SIGNAL CIRCUIT SHORT TO GROUND
BRAKE FLUID LEVEL SWITCH
ANTI-LOCK BRAKE MODULE
TEST ACTION APPLICABILITY
1NOTE: Before proceeding, verify that the brake fluid is at the proper level
in accordance with the Service Information.
Turn the ignition on.
With the DRBIIIt, read DTCs.
With the DRBIIIt, erase DTCs.
Turn the ignition off.
Turn the ignition on.
With the DRBIIIt, read DTCs.
Does the DRBIIItdisplay BRAKE FLUID LEVEL?All
Ye s!Go To 2
No!Go To 4
2NOTE: The brake fluid must be at the proper level. Verify that the brake
fluid is at the proper level in accordance with the Service Information.
Turn the ignition off.
Disconnect the Brake Fluid Level Switch harness connector.
Measure the resistance between the terminals of the Brake Fluid Level Switch.
Is the resistance below 5.0 ohms?All
Ye s!Replace the Brake Fluid Level Switch in accordance with the
Service Information.
No!Go To 3
3 Turn the ignition off.
Disconnect the Brake Fluid Level Switch harness connector.
Disconnect the Instrument Cluster C2 harness connector.
Measure the resistance between ground and the Brake Fluid Level Switch signal
circuit.
Is the resistance below 5.0 ohms?All
Ye s!Repair the Brake Fluid Level Switch signal circuit for a short to
ground.
No!Replace the Antilock Brake Module in accordance with the
Service Information.
13
BRAKES (CAB)

Symptom:
BRAKE SWITCH CIRCUIT
When Monitored and Set Condition:
BRAKE SWITCH CIRCUIT
When Monitored: Ignition On - Continuously
Set Condition: When the brake lamp switch and brake switch outputs are both open or
shorted.
POSSIBLE CAUSES
INTERMITTENT BRAKE SWITCH CIRCUIT DTC
BRAKE LAMP SWITCH STATUS
BRAKE SWITCH STATUS
FUSED IGNITION SWITCH OUTPUT CIRCUIT OPEN
OUTPUT CIRCUIT SHORT TO VOLTAGE
OUTPUT CIRCUIT SHORT TO GROUND
OUTPUT CIRCUIT OPEN
BRAKE SWITCH OUTPUT CIRCUIT SHORT TO BRAKE LAMP SWITCH OUTPUT CIRCUIT
BRAKE LAMP SWITCH
BRAKE SWITCH
ANTI-LOCK BRAKE CONTROLLER
TEST ACTION APPLICABILITY
1NOTE: This DTC will set if the Brake Switch, the Brake Lamp Switch, or
both switches are inoperative. It will be necessary to verify the functional-
ity of each switch.
NOTE: If the Brake Switch and the Brake Lamp Switch are inoperative, it
will be necessary to diagnose BOTH circuits.
Turn the ignition off.
Turn the ignition on.
With the DRBIIItin Inputs/Outputs, monitor the Brake Lamp Switch state while
pressing and releasing the brake pedal.
Does the DRBIIItdisplay change from OPEN to CLOSED as the brake pedal is
pressed and released?All
Ye s!Go To 2
No!Go To 5
17
BRAKES (CAB)

TEST ACTION APPLICABILITY
2NOTE: This DTC will set if the Brake Switch, the Brake Lamp Switch, or
both switches are inoperative. It will be necessary to verify the functional-
ity of each switch.
NOTE: If the Brake Switch and the Brake Lamp Switch are inoperative, it
will be necessary to diagnose BOTH circuits.
Turn the ignition off.
Turn the ignition on.
With the DRBIIItin Inputs/Outputs, monitor the Brake Switch state while pressing
and releasing the brake pedal.
Does the DRBIIItdisplay change from CLOSED to OPEN as the brake pedal is
pressed and released?All
Ye s!Go To 3
No!Go To 4
3 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.
Were any problems found?All
Ye s!Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1.
No!Test Complete.
4 Turn the ignition off.
Disconnect the C1 Brake Switch harness connector.
Turn the ignition on.
With the DRBIIItin Inputs/Outputs, monitor the Brake Switch state.
Connect a jumper wire between the Fused Ignition Switch Output circuit and Brake
Switch Output circuit in the C1 Brake Switch harness connector.
Does the DRBIIItdisplay a change from OPEN to CLOSED?All
Ye s!Replace the Brake Switch in accordance with the Service Infor-
mation.
Perform ABS VERIFICATION TEST - VER 1.
No!Go To 6
5 Turn the ignition off.
Disconnect the C2 Brake Lamp Switch harness connector.
Turn the ignition on.
With the DRBIIItin Inputs/Outputs, monitor the Brake Lamp Switch state.
Connect a jumper wire between the Fused Ignition Switch Output circuit and Brake
Lamp Switch Output circuit in the C2 Brake Lamp Switch harness connector.
Does the DRBIIItdisplay a change from OPEN to CLOSED?All
Ye s!Replace the Brake Lamp Switch in accordance with the Service
Information.
Perform ABS VERIFICATION TEST - VER 1.
No!Go To 6
18
BRAKES (CAB)
BRAKE SWITCH CIRCUIT ÐContinued

Symptom:
CAB CHECK SUM
When Monitored and Set Condition:
CAB CHECK SUM
When Monitored: Ignition On - Once
Set Condition: When the sum of all storage bytes are not equal to the original sum stored.
POSSIBLE CAUSES
INTERMITTENT CAB CHECK SUM DTC
DAMAGED CAB/CAB HARNESS CONNECTOR
FUSED OPTIONAL EQUIPMENT RELAY OUTPUT CIRCUIT OPEN
FUSED B(+) CIRCUIT OPEN
GROUND CIRCUIT OPEN
ANTI-LOCK BRAKE CONTROLLER
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, read DTCs.
With the DRBIIIt, erase DTCs.
Turn the ignition off.
Turn the ignition on.
With the DRBIIIt, read DTCs.
Does the DRBIIItdisplay CAB CHECK SUM?All
Ye s!Go To 2
No!Go To 6
2 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 3
21
BRAKES (CAB)

Symptom:
CAB OPTION
When Monitored and Set Condition:
CAB OPTION
When Monitored: Ignition On - Once
Set Condition: When the vehicle line information transmitted does not match the
expected values.
POSSIBLE CAUSES
INTERMITTENT CAB OPTION DTC
DAMAGED CAB/CAB HARNESS CONNECTOR
FUSED OPTIONAL EQUIPMENT RELAY OUTPUT CIRCUIT OPEN
FUSED B(+) CIRCUIT OPEN
GROUND CIRCUIT OPEN
ANTI-LOCK BRAKE CONTROLLER
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, read DTCs.
With the DRBIIIt, erase DTCs.
Turn the ignition off.
Turn the ignition on.
With the DRBIIIt, read DTCs.
Does the DRBIIItdisplay CAB OPTION?All
Ye s!Go To 2
No!Go To 6
2 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 3
23
BRAKES (CAB)