WORKHORSE CUSTOM CHASSIS
Service Manual
Automatic Transmission – Allison
2007 W Series
© 2006 Workhorse Custom Chassis — All Rights Reserved
SECTION
7.2
PAGE
275
2007 W Series Chassis
WSM082106
DTC P0842
Step
Action
Yes
No
7
1. Connect the AT inline 20-way connector.
2. Remove the transmission oil pan. Refer to Oil Pan Replacement .
3. Disconnect the AT internal wiring harness from the PSM and ground terminal A.
Does the scan tool indicate PS1 status is LOW when grounded and HIGH when open?
Go to Step 8
Go to Step 10
8
1. Remove the PSM from the control valve body and leave the internal harness
connected. Refer to Pressure Switch Manifold Replacement .
2. Provide a ground connection for the PSM to either the control valve body or the
transmission main case.
3. Using the eraser end of a pencil, push gently on the PS1 membrane.
Does the scan tool indicate PS1 status is LOW when grounded and HIGH when open?
Go to Diagnostic Aids
Go to Step 9
9
Replace the PSM. Refer to Pressure Switch Manifold Replacement .
Did you complete the replacement?
Go to Step 13
—
10
Replace the AT internal wiring harness. Refer to Wiring Harness Replacement .
Did you complete the replacement?
Go to Step 13
—
11
Test the PS1 circuit between the TCM and AT inline 20-way connector for an open or
short condition. Refer to Circuit Testing .
Did you find and correct the condition?
Go to Step 13
—
12
IMPORTANT:
Prior to replacing the TCM, swap the TCM with a known good TCM.
Prior to replacing the TCM, swap the TCM with a known good TCM.
In most cases, the TCM is not at fault. Investigate thoroughly before
In most cases, the TCM is not at fault. Investigate thoroughly before
replacing the TCM.
replacing the TCM.
Replace the TCM. Refer to Control Module References for replacement, setup, and
programming.
Did you complete the replacement?
Go to Step 13
—
