WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
256
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
DTC P0777
Circuit Description
Pressure control solenoid 2 (PCS2) is used to control
on-coming, off-going, and holding pressure to any
1 of the 5 clutches. This solenoid is referred to as a
pressure proportional to current (PPC) solenoid since
the output hydraulic pressure supplied by this solenoid is
proportional to the controlled current command.
The transmission control module (TCM) uses
information from the turbine and output speed sensors
(OSS) to detect if a clutch is in a tie-up condition or 3
clutches are applied. The clutch being controlled by
PCS2 will vary, depending on the shift being made.
DTC P0777 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
• DTC P0777 Pressure Control Solenoid 2 (PCS2) Stuck
On
Conditions for Running the DTC
• DTCs P0716, P0717, P0721, P0722, P0875, and P0876
are not active.
• The components are powered and ignition voltage is
greater than 9.0 volts and less than 18 volts.
• Output speed is greater than 200 RPM.
• Turbine speed is greater than 200 RPM.
Conditions for Setting the DTC
DTC P0777 sets when the TCM detects the off-going clutch,
controlled by PCS2, remains engaged during a forward range
shift.
Action Taken When the DTC Sets
• The TCM illuminates the malfunction indicator lamp
(MIL).
• When failure occurs in a forward range, the transmission
will go to the previous range. If failure occurs in
NEUTRAL or REVERSE, the transmission will lock in
NEUTRAL while diagnostic response is active.
• If the shift selector is moved to NEUTRAL, the
transmission will shift to NEUTRAL.
• If the shift selector is moved to REVERSE, the
transmission will shift to REVERSE or NEUTRAL or in
some cases may lock in NEUTRAL.
• If the shift selector is returned to a forward range and
the transmission is compromised by overspeeding or
direction change, the transmission will shift to NEUTRAL.
• DTC P0777 is stored in TCM history.
• The TCM freezes shift adapts.
• The TCM inhibits torque converter clutch (TCC)
engagement.
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
