WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
258
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
DTC P0777
Step
Action
Value
Yes
No
Schematic Reference: Automatic Transmission Controls Schematics
1
Did you perform the Diagnostic System Check - Vehicle?
—
Go to Step 2
Go to Diagnostic
System Check - Vehicle
2
Measure the transmission fluid level. Refer to Transmission Fluid Checking .
Is the transmission fluid level correct?
Go to Step 3
Go to Transmission
Fluid Checking
3
1. Install the scan tool.
2. Start the engine.
IMPORTANT:
Before clearing the DTC, use the scan tool in order to record
Before clearing the DTC, use the scan tool in order to record
the Freeze Frame and Failure Records for reference. The
the Freeze Frame and Failure Records for reference. The
Clear Info function will erase the data.
Clear Info function will erase the data.
3. Record the DTC Freeze Frame and Failure Records.
4. Clear the DTC.
5. Using the scan tool, measure ignition voltage.
Is the voltage within the specified range?
9-18 V Go to Step 4
Go to DTC P0562 for
low voltage or DTC
P0563 for high voltage
4
1. Start the engine.
2. Drive the vehicle under normal operating conditions.
3. Using the scan tool, monitor engine, turbine and OSS readings.
Is speed sensor data erratic?
—
Go to the appropriate
speed sensor DTC
Go to Step 5
5
1. Connect a 2 000 kPa (300 psi) pressure gage to the line pressure tap.
Refer to Line Pressure Check Procedure.
2. Using the scan tool in clutch test mode, cycle through all transmission
ranges with the engine at idle and vehicle brakes applied. Record line
pressure in each range.
Was the line pressure low in a specific range or in ranges where the same
clutch was applied?
—
Go to Low Main Line
Pressure in All Ranges
Go to Step 6