Fault Code Guide

place if necessary. Check the wiring to warning light
and repair or replace the wiring as needed. When
checking the warning light:
• Replace the bulb;
• Check for a fault in the warning lamp circuit,
use ServiceLink or Meritor PC-based diagnos-
tics;
The ABS system needs between 9.5 and 14 volts.
NOTE: Wire repairs may require the use of spe-
cial tools for certain connectors and terminals.
See Group 54 for information on special termi-
nals and connectors and ordering tools for
them.
See the wiring diagrams in Specifications 400 when
troubleshooting the ABS system. If a fault cannot be
repaired or erased from ECU memory, contact your
District Service Manager or call Meritor WABCO at
1-800-535-5560.
Erasing a Fault from the ECU
Memory
NOTE: An active fault cannot be erased until it
has been corrected.
Meritor WABCO recommends that you erase all
faults from the ECU memory after they have been
noted and corrected.
Stored faults are erased from the ECU memory by
clearing historic faults in ServiceLink or Meritor Tool-
box.
Reset Memorized (Learned
Components)
The ECU learns whether or not a retarder interrupt
circuit is present. Once the ECU has detected a re-
tarder circuit, it expects to see it every time the ve-
hicle is powered up and will monitor the circuit for
faults. If the ECU senses a resistance on the retarder
circuit it will automatically learn that the retarder cir-
cuit exists. If an engine retarder circuit does not
exist, but the ECU has detected one and is indicating
faults, something may have been connected (a multi-
meter, etc.) to the retarder circuit during testing.
Moisture, faulty circuit wiring, or moving an ECU from
one vehicle to another can also cause the ECU to
mistakenly detect a non-existent retarder circuit. If
necessary, use the "Reset Memorized" command in
the Meritor WABCO TOOLBOX Software to clear the
ECU memory of this component. For instructions,
see
Meritor WABCO Maintenance Manual No. 39,
Rev. 1/00
.
Power Distribution Module
The main power distribution module (PDM) is
mounted in the engine compartment on the left front
quarter fender. See Fig. 6 for the location of Fuse
16, ABS constant battery power. See Group 54 for
complete PDM information.
Bulk Head Module
The Bulkhead Module (BHM) is the primary module
of the vehicle electrical system, and controls the op-
eration of the other multiplex modules in the system
and a variety of other vehicle components either di-
rectly or indirectly.
OFF
OFF
OFF
OFF
ON
ON
ON
Ignition
key ON
Time
A
B
C
D
A
08/19/2002 f040633
A. Normal Condition
B. Bulb or Wiring Problem
C. Connector, Wiring or ECU (warning light circuit
problem)
D. ABS Fault
Fig. 2, ABS Warning Lamp Conditions
Meritor WABCO Hydraulic Antilock Braking System (ABS) 42.26
Troubleshooting
Business Class M2 Workshop Manual, Supplement 4, March 2003300/2