Chevrolet Low Cab Forward 6.0L Gasoline Engine 3500/4500 Series (GMNA-
Localizing-U.S.-12533400) - 2019 - CRC - 11/19/18
Instruments and Controls
75
The warning light and buzzer will
come on simultaneously when the
brake booster
’
s vacuum or pressure
becomes insufficient either during
driving or when the engine control
switch is in the ON position, or when
there is an abnormality in the
charging system, such as an
alternator malfunction or loosening
or splitting of the fan belt or
whenever the hydraulic brake
booster (HBB) becomes faulty. The
warning buzzer will stop sounding
when the parking brake is engaged.
On 4500, the brake low vacuum
warning light and warning buzzer
should come on to indicate low
vacuum reserve for brake power
assist. At the same time, the Back
up Electric Vacuum Pump operates.
4500 models are equipped with a
Back up Electric Vacuum Pump that
will turn on if brake booster vacuum
becomes insufficient.
If this happens while driving:
.
Do not pump the brakes. The
system is designed to stop the
truck with reserve power assist if
the pedal is held down. This
reserve is greatly reduced each
time you apply and release the
brakes.
.
Stopping distance may be
longer.
.
You may have to push much
harder on the brake pedal.
.
Have the vehicle repaired before
you continue driving.
The buzzer stops when the selector
lever is shifted to the P position.
{
Warning
Do not drive while the buzzer
sounds as the brakes are not
operating to their full capacity.
You and others could be seriously
injured.
Antilock Brake System
(ABS) Warning Light
This light comes on briefly when the
engine control switch is turned to
the ON position, and then should go
out after approximately
three seconds. If the light does not
come on, have it fixed so it will be
ready to warn if there is a problem.
This warning light comes on
together with the brake system
warning light whenever there is a
problem in the Anti-lock Brake
System (ABS). In this case, the ABS
stops working but the brakes still
function as ordinary service brakes.
