2ML70 - Automatic Transmission
DTC P0973 or P0974
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructionsprovides 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 1 is part of the control solenoid valve assembly and is not serviced separately. The control solenoid valve assembly supplies 12 V to shift solenoid 1 on the high side driver 1 circuit. The control solenoid valve assembly controls the normally closed shift solenoid 1 on the shift solenoid 1 control circuit. The shift solenoid 1 controls the transmission fluid to the hybrid low, 1-2 clutch boost valve assembly.
In the OFF position, shift solenoid 1 controls the transmission fluid to the following components:
* EVT 1 mode, oil is supplied to drive motors with generator 1 and 2 for cooling and the hybrid low, 1-2 clutch
* EVT 2 mode, oil is supplied to drive motors with generator 1 and 2 for cooling and the hybrid direct 2-3-4 clutch
In the ON position, shift solenoid 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 vehicle speed is less than 200 km/h (124 mph) for 5 seconds.
* The system voltage is 11-18 V.
Conditions for Setting the DTC
P0973
The control solenoid valve assembly detects an internal low voltage electrical malfunction of the shift solenoid 1 control circuit when shift solenoid 1 is commanded OFF for 1 second.
P0974
The control solenoid valve assembly detects an internal high voltage electrical malfunction of the shift solenoid 1 control circuit when shift solenoid 1 is commanded ON for 1 second.
Action Taken When the DTC Sets
* DTCs P0973 and P0974 are Type A DTCs.
* The transmission control module defaults the transmission to EVT 1 or EVT 2 depending on vehicle speed.
* The transmission control module commands maximum line pressure.
* The transmission control module 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 valve assembly is warmed up and the transmission is operated long enough to ensure a 3°C (37°F) increase in TCM temperature parameter. This will place the transmission control module under the optimal conditions to test solenoid electrical DTCs.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics 2ML70 - Automatic Transmission
Connector End View Reference
Component Connector End Views Connector End Views By Name
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Programming and Relearningfor scan tool information.
Circuit/System Verification
1. Engine ON, verify the transmission fluid temperature is between 50-80°C (122-176°F).
2. Operate the vehicle with the transmission in M1 range long enough to verify at least a 3°C (37°F) rise in TCM temperature parameter, then operate the vehicle in Park for 5 seconds.
3. Engine ON, observe the scan tool Shift Sol. 1 CKT Status parameter. The reading should display OK or Indeterminate.
• If the reading is not within the specified range, replace the Q8 control solenoid valve assembly.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Control Module References Programming and Relearningfor Control Solenoid Valve Assembly replacement, programming and setup.