PART 8: MAINTENANCE AND SERVICE ANTI-LOCK BRAKING SYSTEM (ABS)
(R10/06) Y53-6007 – 191 –
hub is reinstalled. On rear axles, the sensor should be
pushed fully into the mounting block before reinstall
-
ing the hub.
• Check ABS wiring harnesses and piping periodically
for chafing or other problems. No regular mainte
-
nance is required on the ABS components.
• During wheel balancing, dyno testing, or any time the
ignition is on with part of the ABS disconnected, a fail
-
ure code will be recorded. After servicing or testing of
the vehicle is completed, clear the failure codes.
If, due to operating conditions, a brake application causes
either wheel on the same axle to begin skidding, wheel
speed sensors immediately signal the anti-lock controller
in the modulator assembly. The controller responds
instantly by signaling the solenoids in the modulator which
activate the air valves, reducing application pressure as
needed to prevent the wheels from locking up. If this over-
riding correction is effective, application pressure is
allowed to build up to the original input.
Any malfunction of the anti-lock system on one or more
axles will cause the system to fail-safe, and the panel-
mounted amber warning light will come on, indicating both
a malfunction, and automatic shut-down of the system. If
the air system is intact (indicated by the pressure
gauges), the service brakes will continue to function nor
-
mally, but without benefit of the anti-lock feature.
WARNING! Although the brakes will continue to
operate with a malfunction in either circuit, the
vehicle should not be operated until the system
is repaired, and both braking circuits, including
all pneumatic and mechanical components, are
working properly.
CAUTION: Do not attempt to recycle the anti-
lock system until the vehicle has been
brought to a full stop.
NOTE: If one wheel on any driven axle continues
to slip or spin for approximately 4 seconds, this
will cause the anti-lock controller for that axle to
go into the fail-safe mode, and the warning light
will give a shutdown signal. In this case, the anti-
lock system can be turned back on, and the warn
-
ing light extinguished, by turning the key switch
OFF and ON, after the vehicle has been brought
to a full stop. When the key switch is turned back
on, the warning light will illuminate and remain on
for 3 to 5 seconds. This is a built-in function test of
the warning light.
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