M99 - Automatic Transmission
DTC P0973 or P0974
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 P0973
- Shift Solenoid (SS) 1 Control Circuit Low Voltage
DTC P0974
- Shift Solenoid (SS) 1 Control Circuit High Voltage
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The shift solenoid (SS) 1 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 1 on the high side driver 1 circuit. The control solenoid (w/body and TCM) valve assembly controls the normally closed SS 1 on the SS 1 control circuit. The SS 1 controls the transmission fluid to the hybrid low, 1-2 clutch boost valve assembly.
In the OFF position, SS 1 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
* EVT 2 mode, oil is supplied to drive motors 1 and 2 for cooling and the hybrid direct 2-3-4 clutch
In the ON position, SS 1 controls the transmission fluid to the following components:
* 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
* 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 1 is commanded ON or OFF.
Conditions for Setting the DTC
DTC P0973
The control solenoid (w/body and TCM) valve assembly detects an internal low voltage electrical malfunction of the SS 1 control circuit when SS 1 is commanded OFF for 300 milliseconds.
DTC P0974
The control solenoid (w/body and TCM) valve assembly detects an internal high voltage electrical malfunction of the SS 1 control circuit when SS 1 is commanded ON for 300 milliseconds.
Action Taken When the DTC Sets
* DTCs P0973 and P0974 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 P0973 and P0974 are Type A DTCs.
Diagnostic Aids
When attempting to set solenoid electrical DTCs, ensure the control solenoid (w/body and TCM) valve assembly is warmed up and the transmission is operated in 2nd gear long enough to ensure a 3°C (5°F) increase in TCM 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 M 1 long enough to ensure at least a 3°C (5°F) rise in TCM temperature.
3. Place the gear selector in D for 5 seconds and then idle vehicle for 5 seconds.
4. Observe the scan tool data parameter Shift Sol. 1 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.