Fault Code Guide

ABS Warning Lamp Function
The ABS warning lamp in the instrument cluster
warns the driver of a malfunction in the anti-lock
brake system. When the system is operating nor-
mally, the lamp should come on for a few seconds
when the ignition is first turned on, then it should turn
off. If a fault occurs in the system, the lamp will illu-
minate as long as the fault remains active. If a wheel
sensor fault is repaired or if the system is reconfig-
ured, the light will remain on until the vehicle is
driven over 4 mph (6.4 km/h).
The ABS warning lamp can be controlled by any of
the following ways:
• By wire (circuit 376L1): The ABS warning
lamp is hardwired between the ABS ECU and
the instrument cluster through a relay. When
the circuit to pin B11 at the instrument cluster
is grounded, the lamp will turn on.
NOTE: The relay is used to invert the ground
signal between the ABS ECU and the instru-
ment cluster (ground at ABS ECU pin = lamp
off, while ground at the instrument cluster pin
B11 = lamp on). It also ensures that the lamp
will be on if the ABS ECU is disconnected from
the vehicle harness.
• J1587 Message: The ABS ECU can send
messages over the J1587 databus to turn the
warning lamp on or off.
• J1939 Message: The ABS ECU can send
messages over the J1939 databus to turn the
warning lamp on and off.
The ABS warning lamp will be illuminated if circuit
376L1 connected to pin B11 at the instrument cluster
or if either J1587 or J1939 databus message is
broadcast to turn on the lamp. Any one of these will
cause the lamp to turn on. See Fig. 1 for ABS lamp
wiring.
The ABS ECU will monitor the hardwired lamp circuit
for faults (the portion that operates the control side of
the relay).
Troubleshooting Tables
Meritor WABCO Pneumatic Antilock Braking System
(ABS)
42.00
ABS Lamp Troubleshooting
Business Class M2 Workshop Manual, Supplement 0, January 2002 310/1