Workhorse ALLISON 1000MH Service Manual page 380

WORKHORSE CUSTOM CHASSIS
Service Manual
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 P0978 is stored in TCM history.
• Main modulation (MAIN MOD) is inhibited..
• 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
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SECTION
7.2 380
• When diagnosing for an intermittent short or open,
• You may have to drive the vehicle in order to experience
• DTC P0978, when set in combination with DTC P0964,
Test Description
The number below refers to the step number on the
diagnostic table.
© 2006 Workhorse Custom Chassis — All Rights Reserved
Automatic Transmission – Allison
– A broken wire inside the insulation
massage the wiring harness while watching the test
equipment for a change.
a condition.
P0972 and P0975, may indicate an open in the actuator
supply voltage 2 circuit.
3. This step tests the command signal from the TCM.
2007 W Series Chassis
2007 W Series