WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
294
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
observe the parameter as you move the shift lever.
The parameter should display Park/Neutral when in
Park or Neutral and In-Gear when in Reverse, Drive or
Drive Low. It is especially important to closely observe
the Park and Neutral to Drive transitional positions
while moving the shift lever and observing for possible
misalignment or slack in the shifter mechanism.
Circuit/System Testing
1. Ignition OFF, transmission in Park or Neutral,
disconnect the transmission 20-way connector.
2. Test for less than 1 ohm of resistance between
the Park/Neutral signal circuit terminal 18 on the
transmission side and ground.
• If greater than the specifi ed range, test the signal
circuit between the connector and the IMS for an
open/high resistance. If the circuit tests normal,
replace the IMS.
3. Ignition On, verify the Park/Neutral parameter displays
In-gear.
• If not the specifi ed value, test the signal circuit for a
short to ground. If the circuit tests normal, replace the
ECM/PCM.
4. Install a fused jumper between the signal circuit and
ground. Verify the Park/Neutral parameter displays
Park/Neutral.
• If not the specifi ed value, test the signal circuit for
a short to voltage or an open/high resistance. If the
circuit tests normal, replace the ECM/PCM.
Repair Instructions
Perform the Diagnostic Repair Verifi cation after
completing the diagnostic procedure.
1. ECM/PCM replacement. Refer to Control Module
References for replacement, setup, and programming.
2. IMS replacement. Refer to Manual Shift Shaft, Detent
Lever, and Position Switch Assembly Replacement .
DTC P0872
Circuit Description
The pressure switch manifold (PSM) is a multiple-
switch assembly made up of 3 normally open (N/O)
pressure switches and 1 normally closed (N/C) pressure
switch. Pressure switch 3 (PS3) monitors shift valve
3 positioning and relays it to the transmission control
module (TCM).
DTC P0872 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
• DTC P0872 Transmission Pressure Switch 3 Circuit Low
Conditions for Running the DTC
• 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.
• Shift valve 3 is commanded to the OFF, destroked,
position.
