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WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
336
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
DTC P0962
Circuit Description
The pressure control solenoid main modulation (MAIN
MOD) is a normally closed (N/C) solenoid used to
modulate transmission main pressure. The transmission
control module (TCM) commands the solenoid ON when
specifi c transmission and engine conditions are met.
When solenoid MAIN MOD is commanded ON, hydraulic
pressure is routed to the main pressure regulator valve,
lowering transmission main pressure.
The TCM provides voltage to the MAIN MOD, torque
converter clutch (TCC) and pressure control solenoid 1
(PCS1) through a separate solid-state device called high
side driver 1 (HSD1). The TCM uses a low side driver to
switch MAIN MOD ON and OFF.
DTC P0962 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
• DTC P0962 Pressure Control Solenoid (PCS) Main
Modulation (MAIN MOD) 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.
• TCM initialization is in process or engine speed is
greater than 200 RPM and less than 7,500 RPM for less
than 5 seconds.
• The TCM must auto-detect the MAIN MOD solenoid for
this test to run.
Conditions for Setting the DTC
DTC P0962 sets when the TCM detects a short to ground condition in
the MAIN MOD solenoid return circuit for greater than 2 seconds.
Action Taken When the DTC Sets
• The TCM illuminates the malfunction indicator lamp
(MIL).
• DTC P0962 is stored in TCM history.
• The TCM inhibits MAIN MOD.
Conditions for Clearing the DTC
A scan tool can clear the code from TCM history. The
TCM automatically clears the DTC from TCM history if
the vehicle completes 40 warm-up cycles without failure.
Diagnostic Aids
• Inspect the wiring for poor electrical connections at the
TCM. Inspect for the following conditions:
– A bent terminal
– A backed-out terminal
– A damaged terminal
– Poor terminal tension
– A chafed wire
– A broken wire inside the insulation
• When diagnosing for an intermittent short or open,
massage the wiring harness while watching the test
equipment for a change.
• You may have to drive the vehicle in order to experience
a condition.