WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
382
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
DTC P0978
Step
Action
Value
Yes
No
5
1. Disconnect the AT inline 20-way connector.
2. Install the J 44152 jumper harness (20 pins) on the transmission
side of the AT inline 20-way connector.
3. Using the DMM and the J 35616 GM terminal test kit, measure the
resistance at terminal C and N of the J 44152 . Refer to Automatic
Transmission Inline Harness Connector End View .
Is the resistance within the specified value?
22.0 ohms at 20°C
(68°F)
Go to Step 7
Go to Step 6
6
1. Remove the transmission oil pan. Refer to Oil Pan Replacement.
2. Remove the AT internal wiring harness at the SS3 connector.
3. Using the DMM, measure the resistance of SS3.
Is the solenoid resistance within the specified value?
22.0 ohms at 20°C
(68°F)
Go to Step 8
Go to Step 9
7
Test the SS3 circuit between the TCM and the AT inline 20-way connector
for an open condition. Refer to Testing for Continuity .
Did you find and correct the condition?
—
Go to Step 11
—
8
Replace the AT internal wiring harness. Refer to Wiring Harness
Replacement .
Did you complete the replacement?
—
Go to Step 11
—
9
Replace the SS3. Refer to Control Valve Solenoid Replacement .
Did you complete the replacement?
—
Go to Step 11
—
10
IMPORTANT:
In most cases, the TCM is not at fault. Investigate thorough-
In most cases, the TCM is not at fault. Investigate thorough-
ly before replacing the TCM. Swap the TCM with a known
ly before replacing the TCM. Swap the TCM with a known
good TCM to confirm diagnosis.
good TCM to confirm diagnosis.
Replace the TCM. Refer to Control Module References for replacement,
setup and programming.
Did you complete the replacement?
—
Go to Step 11
—
