P0773

ALLISON AUTOMATIC TRANSMISSION

DTC P0773
Circuit Description for Allison Automatic Transmission
Shift E solenoid is a normally closed (N/C) solenoid that provides control main pressure to stroke the E shift valve. The transmission control module (TCM) determines the proper solenoid command logic to move the E shift valve to attain a particular range.

Since the valve state, stroked or unstroked, is critical to providing the correct transmission range, the shift valve has a pressure switch, located in the pressure switch manifold, to provide feedback to the TCM as to the position of the valve.

DTC P0773 is a type A DTC.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0773 Torque Converter Clutch (TCC) Enable Solenoid Control Circuit

Conditions for Running the DTC
^ The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
^ TCM initialization is in process or engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds.

Conditions for Setting the DTC
DTC P0773 sets when the TCM detects any one of the following conditions for greater than 100 milliseconds:
^ An open circuit or a short to ground is detected when E solenoid is commanded OFF.
^ A short to power is detected when E solenoid is commanded ON.

Action Taken When the DTC Sets
^ The TCM illuminates the malfunction indicator lamp (MIL).
^ When in a forward range, the transmission will shift to another forward range while diagnostic response is active.
^ If the shift selector is moved to NEUTRAL, the transmission will shift to NEUTRAL.
^ If the shift selector is moved to REVERSE, the transmission will shift to NEUTRAL or REVERSE.
^ If the shift selector is returned to a forward range and the transmission is compromised by over speeding or direction change, the transmission will lock in NEUTRAL.
^ DTC P0773 will be stored in TCM history.
^ The TCM freezes shift adapts.
^ The TCM inhibits torque converter clutch (TCC) engagement.

Conditions for Clearing the DTC
A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.

Diagnostic Aids
^ Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:
- A bent terminal
- A backed-out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation
^ When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
^ You may have to drive the vehicle in order to experience a condition.
^ Solenoids are sensitive to battery voltage spikes and poor ground connections. This condition may not be indicated with your scan tool, or with a DMM.

Test Description








The numbers below refer to the step numbers on the diagnostic table.
This step tests ignition voltage.
This step tests the command signal from the TCM.
This step tests the resistance value of the external harness and solenoid.
This step tests the resistance value of the solenoid, and tests the internal wiring harness for opens/shorts.

This step tests the resistance value of the solenoid.