WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
394
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
DTC P1688
Step
Action
Yes
No
7
Replace the ECM. Refer to Control Module References for replacement, setup, and
programming.
Did you complete the replacement?
Go to Step 8
—
8
Perform the following procedure in order to verify the repair:
1. Select DTC.
2. Select Clear Info.
3. Operate the vehicle under the following conditions:
– Vehicle at operating temperature
– Engine speed greater than 200 RPM
– All conditions are met for 2 seconds
4. Select Specific DTC.
5. Enter DTC P1688.
Has the test run and passed?
Go to Step 9
Go to Step 2
9
With the scan tool, observe the stored information, capture info and DTC info.
Does the scan tool display any DTCs that you have not diagnosed?
Go to Diagnostic
Trouble Code (DTC)
List - Vehicle
System OK
DTC P1779
Circuit Description
Vehicles currently using the 8.1 liter gas engine use
a 3 wire system to communicate engine torque data/
requests between the engine control module (ECM) and
the transmission control module (TCM).
DTC P1779 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1779 Engine Torque Delivered to Transmission
Control Module (TCM) Signal
Conditions for Running the DTC
• The components are powered and ignition voltage is
greater than 9.0 volts and less than 18 volts.
• Engine speed is greater than 200 RPM and less than
7,500 RPM for 5 seconds.
Conditions for Setting the DTC
DTC P1779 sets if managed engine torque, net, signal
is less than 1.5 percent or greater than 98.5 percent for
greater than 2 seconds.
