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WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
398
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
DTC P2670
Circuit Description
The transmission control module (TCM) provides
voltage to shift solenoid 1, 2, and 3 (SS1, SS2, and
SS3) and pressure control solenoid 2 (PCS2) through
a separate solid-state device called high side driver
2 (HSD2). HSD2 is continuously ON during normal
operation, except during a brief circuit test. The TCM
regulates control current to the solenoids by switching
the appropriate low side driver ON and OFF.
DTC P2670 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
• DTC P2670 Actuator Supply Voltage 2 Low
Conditions for Running the DTC
• The components are powered and ignition voltage is
greater than 9.0 volts and less than 18 volts.
• HSD2 is commanded ON.
Conditions for Setting the DTC
DTC P2670 sets when the TCM detects a low voltage
condition, less than 6.0 volts, in 3 solenoids in the HSD2
circuit.
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 P2670 is stored in TCM history.
• The TCM inhibits main modulation (MAIN MOD).
• 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
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.