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GENERAL INFORMATION
3.3.7 TRACTION CONTROL OPERATION
(IF EQUIPPED)
The Anti-lock Brake Module (ABM) monitors
wheel speeds. If, during acceleration, the module
detects front (drive) wheel slip and the brakes are
not applied, the ABM will enter traction control
mode. Traction control works in the following order
when drive wheel slip is detected.
1. Close the (normally open) isolation valves.
2. Start pump/motor and supply volume/pressure
to front hydraulic circuits (pump runs continu-
ously during traction control).
3. Open and close build and decay valves to main-
tain minimum wheel slip and maximum trac-
tion.
The cycling of the build and decay valves is
similar to the ABS except that they work to control
wheel spin by applying brakes. ABS function is to
control wheel skid by releasing brakes.
Two pressure relief valves allow excess fluid vol-
ume to return to the reservoir when not used by the
build/decay cycles. These are required because the
pump supplies more volume than the traction con-
trol system requires.
If at any time the brake pedal is applied during a
traction control cycle, the brake lamp switch will
trigger the ABM to switch off the traction control.
The traction control system will be enabled at
each ignition cycle. It may be turned off by depress-
ing the Traction Control Switch. The traction con-
trol system function lamp will illuminate Traction
Control immediately upon depressing the traction
control switch button. The indicator will illuminate
during a traction control event.
If the ABM calculates that the brake tempera-
tures are high, the traction control system will
become inoperative until a time-out period has
elapsed. When in this thermal protection mode, the
traction control indicator will illuminate; however,
a fault will not be registered.
3.5 DIAGNOSTIC TROUBLE CODES
The Anti-lock Brake Module may report any of
several Diagnostic Trouble Codes (DTC)s.
3.6 FREEZE FRAME
Freeze Frame takes a "snapshot" of specific vehi-
cle information the instant an ABS failure is recog-
nized and stores this information into the ABM
memory. This information can be accessed using the
DRBIII to help diagnose the fault. Freeze Frame
will capture the first time failure or only a new
failure that occurs during the current ignition cycle.
3.7 DRBIII ERROR MESSAGES AND
BLANK SCREEN
Under normal operation, the DRBIII will dis-
play one of only two error messages:
– User-Requested
Requested COLD Boot.
If the DRBIII
should display any other error
message, record the entire display and call the
STAR Center. This is a sample of such an error
message display:
ver: 2.14
date: 26 Jul93
file: key_itf.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.
3.7.1 DRBIII DOES NOT POWER UP
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
connector cavity 16). A minimum of 11 volts is
required to adequately power the DRBIII .
If all connections are proper and the vehicle
battery is fully charged, an inoperative DRBIII
may be the result of faulty cable or vehicle wiring.
3.7.2 DISPLAY IS NOT VISIBLE
Low temperatures will affect the visibility of the
display. Adjust the contrast to compensate for this
condition.
4
WARM
Boot
or
User-
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