Technical information

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25
Technician Guidelines for Antilock Braking Systems
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TABLE 2: COMMON ABS ERRORS AND RESPONSES
DETECTED ERROR SYSTEM RESPONSE
Component or wiring failure
ABS malfunction indicator lamp informs
driver of fault. Affected wheel(s) is
removed from ABS control and switched
to normal braking. The remaining ABS
valves may continue providing braking
control at the wheels. The error is
recorded as a fault code and stored in
the ECU. The information can be recalled
by the technician through the blink code
lamp or an electronic diagnostic tool.
Power supply to ECU is interrupted or
ABS connector not plugged in.
All antilock and traction control systems
would be inoperative. Normal, non-ABS
controlled braking would be available at
all wheels. ABS malfunction indicator
lamp indicates system fault.
Individual electronic component fails
internally in ECU.
All or part of the ABS is shut off and that
part of the vehicle reverts to normal,
non-ABS braking. ABS malfunction
indicator lamp indicates system fault.
Error not detected. ABS remains
inoperative but warning light remains off
Certain failures, mainly mechanical, can
occur and cause the ABS to malfunction
but not illuminate the indicator lamp.
Depending on the fault, the ABS will be
inoperable on one or more axles. In the
rare event a valve hangs open, system
air could be lost, impairing all braking.
Chart 3 on page 24 shows an ABS indicator lamp diagnostic
flow chart. Table 2 on page 25 offers a list of common ABS
errors and responses.
4. Causes of Common ABS Sensor Problems
Table 3 on page 26 summarizes the causes of several
common ABS sensor problems.
One benefit of monitoring wheel speed with a exciter ring/
sensor system is that dirt or dust does not affect operation.