WORKHORSE CUSTOM CHASSIS
Service Manual
Automatic Transmission – Allison
2007 W Series
© 2006 Workhorse Custom Chassis — All Rights Reserved
SECTION
7.2
PAGE
417
2007 W Series Chassis
WSM082106
DTC P2729
Circuit Description
The pressure control solenoid 1 (PCS1) is a pressure
proportional to current (PCC) solenoid used to control
on-coming, off-going and holding pressure to any 1 of
the 5 clutches. The transmission control module (TCM)
provides voltage to the main modulation (MAIN MOD),
torque converter clutch (TCC) and PCS1 through a
separate solid-state device called high side driver 1
(HSD1). The TCM regulates the amount of current to the
PCS1 by switching the low side driver ON and OFF.
DTC P2729 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
• DTC P2729 Pressure Control Solenoid 1 (PCS1) Control
Circuit Low (A)
Conditions for Running the DTC
• DTC P0658 and P0659 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.
• TCM initialization is in process.
• Engine crank time is not extended.
Conditions for Setting the DTC
DTC P2729 sets when the TCM detects a short to
ground on the PCS1 circuit for greater than 2 seconds.
Action Taken When the DTC Sets
• The TCM illuminates the malfunction indicator lamp
(MIL).
• If the failure occurs while in a forward range, a shift to
1st, 3rd or 5th range is made.
• 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. If the shift
selector is moved to a forward range or to REVERSE
and the transmission is compromised by overspeeding or
direction change, the transmission will shift to NEUTRAL.
• DTC P2729 is stored in TCM history.
• The TCM inhibits MAIN MOD.
• 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
TCM. Inspect for the following conditions:
– A bent terminal
– A backed-out terminal
– A damaged terminal
– Poor terminal tension
– A chafed wire
