M99 - Automatic Transmission

DTC P0976 or P0977

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.



DTC Descriptor
DTC P0976
- Shift Solenoid (SS) 2 Control Circuit Low Voltage

DTC P0977
- Shift Solenoid (SS) 2 Control Circuit High Voltage




Diagnostic Fault Information






Typical Scan Tool Data






Circuit/System Description

The shift solenoid (SS) 2 is part of the control solenoid (w/body and TCM) valve assembly and is not serviced separately. The control solenoid (w/body and TCM) valve assembly supplies 12 volts to SS 2 on the high side driver 1 circuit. The control solenoid (w/body and TCM) valve assembly controls the normally closed SS 2 on the SS 2 control circuit. The SS 2 controls the transmission fluid to the 1-3 clutch regulator valve assembly.


In the OFF position, SS 2 controls the transmission fluid to the following components:

* EVT 1 mode, oil is supplied to drive motors 1 and 2 for cooling and the hybrid low, 1-2 clutch
* Gear 1, oil is supplied to the hybrid low, 1-2 clutch and the 1-3 clutch
* Gear 2, oil is supplied to the hybrid low, 1-2 clutch and the hybrid direct 2-3-4 clutch


In the ON position, SS 2 controls the transmission fluid to the following components:

* EVT 2 mode, oil is supplied to drive motors 1 and 2 for cooling and the hybrid direct 2-3-4 clutch
* Gear 3, oil is supplied to the hybrid direct 2-3-4 clutch and the 1-3 clutch
* Gear 4, oil is supplied to the hybrid direct 2-3-4 clutch and the 4th clutch



Conditions for Running the DTC

* The engine run time is greater than 5 seconds.
* The SS 2 is commanded ON or OFF.



Conditions for Setting the DTC

DTC P0976

The TCM detects an internal low voltage electrical malfunction of the SS 2 control circuit when the SS 2 is commanded OFF for 300 milliseconds.

DTC P0977

The TCM detects an internal high voltage electrical malfunction of the SS 2 control circuit when the SS 2 is commanded ON for 300 milliseconds.


Action Taken When the DTC Sets

* DTCs P0976 and P0977 are Type A DTCs.
* The TCM defaults the transmission to EVT 1 or EVT 2 depending on vehicle speed.
* The TCM commands maximum line pressure.
* The TCM freezes transmission adaptive functions.



Conditions for Clearing the DTC

DTCs P0976 and P0977 are Type A DTCs.


Diagnostic Aids

When attempting to set solenoid electrical DTCs, ensure the TCM is warmed up and the transmission is operated in 4th gear long enough to ensure a 3°C (5°F) increase in TCM substrate temperature. This will place the TCM under the optimal conditions to test solenoid electrical DTCs.


Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views
Electrical Information Reference

* Circuit Testing
* Connector Repairs
* Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs
* High Voltage Disabling
* High Voltage Enabling

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference

* Scan Tool Output Controls (Scan Tool Output Controls)
* Scan Tool Data List (Scan Tool Data List)
* Scan Tool Data Definitions (Scan Tool Data Definitions)



Circuit/System Testing

1. Ensure the transmission fluid temperature is between 50 and 80°C (122 and 176°F).
2. Operate the vehicle in 4th gear long enough to ensure at least a 3°C (5°F) rise in TCM temperature.
3. Observe the scan tool data parameter Shift Sol. 2 CKT Status. The parameter should display OK.

• If the parameter displays Open, Short to Volts, Short to GND, or if the DTC resets, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and TCM Assembly Solenoid Performance Test) .
• If no concerns are found during the inspection, replace the control solenoid (w/body and TCM) valve assembly.




Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


Control solenoid (w/body and TCM) valve assembly replacement. Refer to Control Module References for replacement, setup, and programming.