WORKHORSE CUSTOM CHASSIS
Service Manual
Automatic Transmission – Allison
2007 W Series
© 2006 Workhorse Custom Chassis — All Rights Reserved
SECTION
7.2
PAGE
173
2007 W Series Chassis
WSM082106
DTC P0717
Circuit Description
The speed sensors are variable reluctance devices
that convert mechanical motion to an AC voltage. Each
sensor consists of a wire coil wrapped around a pole
piece that is adjacent to a permanent magnet. These
elements are contained in a housing that is mounted
adjacent to a rotating ferrous member, such as a gear
tooth. 2 signal wires extend from one end of the housing
and an exposed end of the pole piece is at the opposite
end of the housing. The permanent magnet produces
lines of fl ux around the pole piece. As a ferrous object,
such as a gear tooth, approaches and passes through
the gap at the end of the pole piece, an AC voltage pulse
is induced in the wire coil. The transmission control
module (TCM) calculates the frequency of these AC
pulses and converts it to a speed value. The AC voltage
generated varies from 150 m volts at low speed to 15
volts at high speed. The signal wires from the sensor are
formed as twisted pairs to cancel magnetically induced
fi elds. The cable is also shielded to protect from voltage
related fi elds. Using 2 wire differential inputs at the TCM
eliminates noise from other sources.
DTC P0717 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
• DTC P0717 Turbine Speed Sensor
Conditions for Running the DTC
• DTC P0721, P0722, P0731, P0732, P0733, P0734,
P0735, and P0736 is not active.
• The components are powered and ignition voltage is
greater than 9.0 volts and less than 18 volts.
• Engine speed is greater than 200 RPM and less than
7,500 RPM for 5 seconds.
• The shift selector indicates a valid range selection except
NEUTRAL.
Conditions for Setting the DTC
DTC P0717 sets when the TCM detects one of the following
conditions:
• An unrealistically large change in turbine speed
• An unrealistically low turbine speed
Action Taken When the DTC Sets
• The TCM illuminates the malfunction indicator lamp
(MIL).
• When failure occurs in a forward range and shifting
is complete, the transmission remains in the current
range. When failure occurs while in a forward range
and the shift is in process, the transmission returns to
the previous range, except in post-shift state, where the
transmission will continue to the commanded range.
When failure occurs in other conditions, the transmission
shifts to 1st, 3rd or 5th. While diagnostic response is
active, if the shift selector is moved to NEUTRAL or
REVERSE, or selecting DRIVE again, the transmission
will lock in NEUTRAL.
• DTC P0717 is stored in TCM history.
