Fault Code Guide
switch is in the air line. A grounded feedback circuit
from the closed pressure switch indicates that the
fifth wheel slide is activated and pressure is being
supplied to the fifth wheel slide air cylinder. An open
feedback circuit indicates that the fifth wheel slide is
not activated, or there is a malfunction; the fifth
wheel slide is turned on but the pressure switch is
still open.
Tag/Pusher Axle Lift
Tag and pusher axles are available on a variety of
M2 vehicles. Tag and pusher axles are free-spinning
axles that are not part of the vehicle drivetrain. Using
air pressure, these axles are raised or lowered on
the vehicle chassis.
When lowered, tag and pusher axles increase the
weight capacity of a vehicle by distributing the ve-
hicle load over more wheels. When increased weight
capacity is not needed, the operator can raise the
axle and save wear on the tires and axle. Tag axles
are located behind the rear drive axles. Pusher axles
are located in front of the rear drive axles. The con-
trol system for operating a tag or pusher axle is com-
monly referred to as axle lift.
Tag and pusher axles may only be lowered at vehicle
speeds slower than 5 mph (8 km/h), but may be
raised at any speed. To avoid damage to a tag or
pusher axle, most axle lift controls automatically raise
the axle when the vehicle is backing up. The tag or
pusher axle returns to the lowered position when the
vehicle is shifted out of reverse.
A vehicle with a reverse caster axle does not auto-
matically raise the axle when backing up. These
axles have air controls that change the caster angle
of the axle to allow the axle to self-steer according to
the direction of travel. Shifting the vehicle into re-
verse prompts the CHM to signal a caster angle
change. With the axle’s caster angle adjusted so that
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1
2
3
4
5
1. Lock Plunger
2. Return Spring
3. Control Linkage
4. Air Cylinder
5. Slide Rail
Fig. 5, Fifth Wheel Slide Assembly
Chassis Electrical Control Systems
54.40
General Information
Business Class M2 Workshop Manual, Supplement 22, September 2012 050/5