WORKHORSE CUSTOM CHASSIS
Service Manual
Automatic Transmission – Allison
2007 W Series
© 2006 Workhorse Custom Chassis — All Rights Reserved
SECTION
7.2
PAGE
169
2007 W Series Chassis
WSM082106
DTC P0716
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 P0716 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
• DTC P0716 Turbine Speed Sensor Circuit Performance
Conditions for Running the DTC
• DTC P0717, P0721 and P0722 are 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 turbine speed is greater than 200 RPM.
Conditions for Setting the DTC
DTC P0716 sets when the TCM detects a large unrealistic change
in turbine speed or if excessive noise is present in the turbine
speed sensor circuit.
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 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 is selecting DRIVE again, the transmission will lock in
NEUTRAL.
• DTC P0716 is stored in TCM history.
• The TCM inhibits torque converter clutch (TCC)
engagement.
