Fault Code Guide

Troubleshooting
Meritor WABCO TOOLBOX
Software
The Meritor WABCO TOOLBOX Software can be
used to diagnose hydraulic antilock brake system
(ABS) faults. This software is packaged and
launched from ServiceLink and provides J1587 fault
codes and on-screen information to make the neces-
sary repairs or replacements. TOOLBOX must be
used to reset the ECU memory. See
Meritor WABCO
Maintenance Manual No. 39, Rev. 1/00
.
ServiceLink
ServiceLink can be used to troubleshoot the Meritor
WABCO hydraulic ABS. J1587 fault codes can be
read by connecting the vehicle to the ServiceLink
computer.
J1587 Fault Codes
The J1587 fault codes are a combination of the mes-
sage identifier (MID), which indicates the ECU or
system with the fault (136 for the hydraulic ABS
ECU), and the system identifier (SID), which indi-
cates the specific component within the system with
the fault. The failure mode indicator (FMI) identifies a
specific problem with the system component. See
Table 1 for a listing of J1587 fault codes. This table
also lists the appropriate troubleshooting table to
consult for fault code diagnosis.
ABS Warning Lamp Circuit
The ABS warning lamp circuit is controlled by wire
alone. It is NOT also controlled by the databus as
with pneumatic ABS vehicles. The ABS lamp cir-
cuit contains a relay located in the dash. The pur-
pose of this relay is to turn on the ABS warning lamp
in the instrument cluster should the ABS controller be
disconnected from the vehicle harness.
When the ignition is turned on, the relay is ener-
gized. This causes the contact to open the circuit
from ground to the instrument cluster (circuit 376L). If
the ABS ECU becomes disconnected from the ve-
hicles harness, the relay becomes de-energized (the
ground provided by circuit 376L1 is now open), thus
causing circuit 376L leading to the instrument cluster
to be grounded through the relay. If a fault occurs in
the ABS under normal operation, the ABS ECU will
ground circuit 376L at pin 8 of the X2 connector, thus
grounding the circuit leading to the instrument cluster
and turning the ABS warning lamp on. See Fig. 1 for
ABS lamp relay wiring detail.
Refer to Fig. 2 to identify a warning lamp condition,
then Fig. 3 to diagnose the condition.
Make the necessary repairs and clear the fault code
from the ECU memory. If more than one fault exists,
it will be displayed after the first one has been
cleared from memory.
A volt ohmmeter (VOM) can determine the condition
of the ABS valves, wheel end sensors and associ-
ated wiring. Figure 4 displays pin locations at the
ECU and Fig. 5 displays pin locations at the ABS
modulator valve. Table 2 and Table 3 display corre-
sponding circuit to pin information.
IMPORTANT: The ignition switch must be off
when connecting or disconnecting the ECU.
NOTE: The blink codes are erased from ECU
memory as repairs are made. Once a repair has
been made, cycle the ignition to ensure the
blink code does not reappear. If there are any
other outstanding faults, the next blink code will
be displayed.
If the ABS light does not operate correctly after the
ignition is turned on (the light does not come on at all
or it does not go out after about 3 seconds), check
all circuit breakers in the control unit panel and re-
08/20/2002 f544126
87a
87
30
B11
ICU
ABS
ECU
X
X
2/8
2/4
376L1
376L
376L
S22
GND
81C
+12V IGNITION
Fig. 1, ABS Lamp Relay Wiring
Meritor WABCO Hydraulic Antilock Braking System (ABS) 42.26
Troubleshooting
Business Class M2 Workshop Manual, Supplement 4, March 2003 300/1