Fault Code Guide

Awake State and Sleep State
The BHM, CHM, and instrumentation control unit
(ICU) are, as a group, in an awake state or a sleep
state depending on vehicle conditions. When any of
these electronic components are awakened, the re-
maining components wake up if they are not already
awake. When the BHM, CHM, and ICU are in an
awake state, the odometer reading appears on the
dash driver display screen.
One of the following actions will cause the BHM,
CHM, or ICU to go into an awake state:
• opening the door switch
• turning on the hazard switch
• turning the ignition switch to any position other
than off
• turning on the headlight/parking light switch
• depressing the service brake
The BHM, CHM, and ICU will enter a sleep state
when they are no longer actively controlling any out-
puts or responding to any inputs and all other power
down requirements are met.
To check whether or not the electrical system is
going into a sleep state:
1. Enter the vehicle.
2. Shut the doors.
3. Remove your foot from the service brake.
4. Make sure the ignition switch and hazard switch
are in the off position.
NOTE: One minute after these conditions are
met, and provided that one of the parameters in
Table 1 has not been added to the BHM, the
odometer reading should disappear. If the
odometer reading does not disappear, the elec-
trical system is not going to sleep.
Expansion Module
The EXM is mounted on the aft chassis. Only one
Expansion Module is available on a vehicle. See
Fig. 3 for an illustration of the Expansion Module.
NOTE: The harness connector numbers on the
CHM and EXM are the same since the hard-
ware for the two modules is the same. However,
the harness connector names for the CHM and
EXM are not the same since the connectors on
the EXM serve different functions than the con-
nectors on the CHM.
The EXM configuration uses external strapping. Ex-
ternal strapping is a process that assigns a unique,
predefined J1939 Source Address and J1587 Mes-
sage ID to the module, which is viewable in Service-
Link
®
.
Parameters
Parameter Part Number Description Hours
26-01017-002 Switched Center Pin Power 24
26-01019-003 Exterior Lighting 16,667
26-01019-004 Exterior Lighting 16,667
26-01019-005 Exterior Lighting 16,667
Table 1, Parameters
03/09/2006
f543900a
Fig. 3, Expansion Module Harness Connectors
Chassis Module and Expansion Module 54.13
General Information
Business Class M2 Workshop Manual, Supplement 10, September 2006050/2