WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
312
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
DTC P0877
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
D.
Does the scan tool indicate PS4 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 pressure switch R membrane.
Does the scan tool indicate PS4 status is LOW when grounded and HIGH when open?
Go to Step 9
Go to Diagnostic Aids
9
Replace the PSM. Refer to Pressure Switch Manifold Replacement .
Did you complete the replacement?
Go to Step 13
Go to Step 10
10
Replace the AT internal wiring harness. Refer to Wiring Harness Replacement .
Did you complete the replacement?
Go to Step 13
11
Test the PS4 circuit between the TCM and the 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