31
Fault
Code
Explanation Possible Causes
PLC
Select
1M
PLC
Select
2M
21
Red channel wheel speed sensor
S1A has an erratic output voltage.
Loose sensor, connection, bracket or
exciter, damaged exciter, sensor is not
properly adjusted or has worn cable
insulation or worn sensor block clip,
wheel bearing failure, wheel bearing is
not properly adjusted (these faults will
only occur at speeds greater than 6
mph).
Measure the AC voltage at the sensor
in question while rotating the wheel at
a rate of about one rotation every two
seconds. The output should be at least
200 millivolts (0.2V AC).
If this is not the case, push in the sensor
until it touches the exciter and rotate
the wheel again. If this doesn’t correct
the problem, then the sensor should be
replaced.
Verify the tire and wheel size is large
enough for 100 tooth exciter ring. If
these faults re-occur at the same speed,
inspect the exciter ring for damage.
Smaller wheels and tires require 80
tooth exciter rings. Reference Tire Scale
Factor Chart.
Verify sensor and valve wiring/plumbing
is correct.
See side-by-side and axle-by-axle
congurations.
X
22
Red channel wheel speed sensor
S1B has an erratic output voltage.
X
23
Blue channel wheel speed sensor
S2A has an erratic output voltage
X
24
Yellow channel wheel speed
sensor S2B has an erratic output
voltage.
X
25
Blue channel wheel speed sensor
S3A has an erratic output voltage.
X
26
Yellow channel wheel speed
sensor S3B has an erratic output
voltage.
X
31
Auxiliary channel 1 fault (digital
channel 1) output only.
PLC Select 2M Plus (ABS
Auxiliary Codes).
Note:
These Codes are only used with PLC
Select 2M Plus ABS that supports trailer
Auxiliaries.
Auxiliary Channel has an open circuit or
the ECU (Electronic Control Unit) has an
auxiliary device connected and is not
programmed to be.
Note: These codes do not affect ABS
performance and do not illuminate the
tractor trailer ABS warning lamps.
32
Auxiliary channel 2 fault (digital
channel 2) output only.
33
Auxiliary channel 3 fault (digital
channel 3) output only.
34
Auxiliary channel 4 fault (digital
channel 4) output only.
35
Auxiliary channel 5 fault (digital
channel 5) output only.
Occurs Only When Vehicle is Stationary