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P0977




DTC P0976 or P0977

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 Instructions)provides an overview of each diagnostic category.

DTC Descriptors
DTC P0976
- 2-3 Shift Solenoid (SS) Control Circuit Low Voltage

DTC P0977
- 2-3 Shift Solenoid (SS) Control Circuit High Voltage

Diagnostic Fault Information





Typical Scan Tool Data






Circuit/System Description

The 1-2 shift solenoid (SS) valve and the 2-3 SS valves control transmission fluid pressure acting on the shift valves to position the valves for the appropriate gear. The 1-2 SS and the 2-3 SS valves are normally-open exhaust valves located on the control valve body. A fused circuit supplies ignition voltage to the 1-2 SS valve and the 2-3 SS valve. The transmission control module (TCM) commands the solenoid ON or OFF by switching the ground path. When the 1-2 SS valve or the 2-3 SS valve is commanded ON, the TCM senses low voltage. When the 1-2 SS valve or the 2-3 SS valve is commanded OFF, the TCM senses high voltage.

Conditions for Running the DTC

The engine speed is greater than 500 RPM for 2 seconds.

Conditions for Setting the DTC

P0976

The TCM detects an open or short to ground on the 2-3 SS valve control circuit for 4.4 seconds.

P0977

The TCM detects a short to voltage on the 2-3 SS valve control circuit for 4.4 seconds.

Action Taken When the DTC Sets

P0976
* DTC P0976 is a Type A DTC.
* The TCM inhibits 1st and 4th gear.
* The TCM commands maximum line pressure.
* The TCM freezes transmission adaptive functions.

P0977
* DTC P0977 is a Type A DTC.
* The TCM inhibits 4th gear.
* 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.

Reference Information
Schematic Reference

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

* Component Connector End Views (Connector End Views By Name)
* Inline Harness Connector End Views (Connector End Views By Number)

Description and Operation

Electronic Component Description (Electronic Component Description)for Shift Solenoid Valves 1-2 and 2-3 information
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 Relearning)for scan tool information
Special Tools

* J 44152 Jumper Harness (20 pins)
* J 44257 Main Wiring Harness Connector Remover

Circuit/System Verification

1. Ignition ON, engine OFF.
2. While observing the 2-3 Sol parameter, command the 2-3 SS ON and OFF using the scan tool special functions. The 2-3 Sol parameter should display OFF when commanded ON, and On when commanded OFF.
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

Important: Additional DTCs may set when disconnecting the automatic transmission inline 20-way connector.


1. Inspect the ECM/TRANS fuse for an open.

• If the fuse is open, test the ignition 1 voltage circuit for a short to ground between the fuse block-underhood and the automatic transmission inline 20-way connector.

• If fuse is not open.

2. Ignition OFF. Using the main wiring harness connector remover J 44257 , disconnect the automatic transmission (AT) inline 20-way connector.
3. Connect the J 44152 jumper harness (20 pins) to the engine side of the connector.
4. Ignition ON. Engine OFF.
5. Using the L-BU probes J 35616-64B, test for B+ (+0.0/-1.0 V) between the ignition 1 voltage circuit, jumper harness terminal E and a good ground, such as the ground terminal of the EL-49742 harness, black terminal.

• If less than the specified value, test the ignition 1 voltage circuit for an open/high resistance, short to ground or short to voltage. If all circuits and connections test normal, test the TCM.

• If B+ (+0.0/-1.0 V).

6. Using the L-BU probes J 35616-64B, test for B+ (+0.0/-1.0 V) between the ignition 1 voltage circuit, jumper harness terminal E and the 2-3 Shift solenoid valve control circuit, jumper harness terminal B.

• If less than the specified value, test the 2-3 Shift solenoid valve control circuit for an open/high resistance, short to ground or short to voltage. If all circuits and connections test normal, test the TCM.

• If B+ (+0.0/-1.0 V).

7. Go to 2-3 Shift Solenoid testing.

Component Testing

2-3 Shift Solenoid
1. Ignition OFF.
2. Using the main wiring harness connector remover J 44257 , disconnect jumper harness J 44152 from the engine side of the AT inline 20-way connector.
3. Install jumper harness J 44152 to the AT 20-way pass-thru connector.
4. Using the L-BU probes J 35616-64B, test for 19-31 ohm between the Ignition 1 Voltage circuit, jumper harness terminal E and the 2-3 Shift Solenoid Valve Control circuit, jumper harness terminal B. Refer to the Component Resistance (Component Resistance) chart.

• If greater than the specified value, test the affected circuits for an open/high resistance condition. If a circuit is shorted or open replace the internal transmission wiring harness assembly, if all circuits and connections test normal replace the 2-3 Shift Solenoid.
• If less than the specified value, test the affected circuits for a shorted together condition. If a circuit is shorted or open replace the internal transmission wiring harness assembly, if all circuits and connections test normal replace the 2-3 Shift Solenoid.

• If between 19-31 ohm.

5. Using the L-BU probes J 35616-64B, test for greater than 1M ohm between the Ignition 1 Voltage circuit, jumper harness terminal E and all other circuits of the jumper harness J 44152 except the 1-2 Shift Solenoid Valve Control circuit, jumper harness terminal A, the 2-3 Shift Solenoid Valve Control circuit, jumper harness terminal B and the Torque Converter Clutch Pulse Width Modulated (TCC PWM) Solenoid Valve Control circuit, jumper harness terminal T.

• If less than the specified value, test the affected circuits for a shorted together condition. If a circuit is shorted or open replace the internal transmission wiring harness assembly, if all circuits and connections test normal replace the 2-3 Shift Solenoid.

• If greater than the specified value.

6. Using the L-BU probes J 35616-64B, test for 19-31 ohm between the Ignition 1 Voltage circuit, jumper harness terminal E and the 1-2 Shift Solenoid Valve Control circuit, jumper harness terminal A. Refer to the Component Resistance (Component Resistance) chart.

• If outside the specified value, test the affected circuits for a shorted together condition. If a circuit is shorted or open replace the internal transmission wiring harness assembly, if all circuits and connections test normal replace the 2-3 Shift Solenoid.

• If between the specified values.

7. Using the L-BU probes J 35616-64B, test for 10-15 ohm between the Ignition 1 Voltage circuit, jumper harness terminal E and the Torque Converter Clutch Pulse Width Modulated (TCC PWM) Solenoid Valve Control circuit, jumper harness terminal T. Refer to the Component Resistance (Component Resistance) chart.

• If outside the specified value, test the affected circuits for a shorted together condition. If a circuit is shorted or open replace the internal transmission wiring harness assembly, if all circuits and connections test normal replace the 2-3 Shift Solenoid.

• If between the specified values.

8. Using the L-BU probes J 35616-64B, test for greater than 1M ohm between the 2-3 Shift Solenoid Valve Control circuit, jumper harness terminal B and all other circuits of the jumper harness J 44152 except the 1-2 Shift Solenoid Valve Control circuit, jumper harness terminal A, the Ignition 1 Voltage circuit, jumper harness terminal E and the Torque Converter Pulse Width Modulated (TCC PWM) Solenoid Valve Control circuit, jumper harness terminal T.

• If less than the specified value, test the affected circuits for a shorted together condition. If a circuit is shorted or open replace the internal transmission wiring harness assembly, if all circuits and connections test normal replace the 2-3 Shift Solenoid Valve.

• If greater than the specified value.

9. Using the L-BU probes J 35616-64B, test for 38-62 ohm between the 2-3 Shift Solenoid Valve Control circuit, jumper harness terminal B and the 1-2 Shift Solenoid Valve Control circuit, jumper harness terminal A. Refer to the Component Resistance (Component Resistance) chart.

• If outside the specified value, test the affected circuits for a shorted together condition. If a circuit is shorted or open replace the internal transmission wiring harness assembly, if all circuits and connections test normal replace the 2-3 Shift Solenoid Valve.

• If between the specified values.

10. Using the L-BU probes J 35616-64B, test for 29-46 ohm between the 2-3 Shift Solenoid Valve Control circuit, jumper harness terminal B and the Torque Converter Pulse Width Modulated (TCC PWM) Solenoid Valve Control circuit, jumper harness terminal T. Refer to the Component Resistance (Component Resistance) chart.

• If outside the specified value, test the affected circuits for a shorted together condition. If a circuit is shorted or open replace the internal transmission wiring harness assembly, if all circuits and connections test normal replace the 2-3 Shift Solenoid Valve.

• If between the specified values.

11. Test for greater than 250K ohm between the following circuits and the transmission case:

* Ignition 1 Voltage circuit, jumper harness terminal E
* 2-3 Shift Solenoid Valve Control circuit, jumper harness terminal B

• If less than the specified value, test the affected circuit for short to the transmission case. If a circuit is shorted or open replace the internal transmission wiring harness assembly, if all circuits test normal, replace the 2-3 Shift Solenoid Valve.

• If greater than the specified value.

12. Go to TCM testing.

TCM
1. Ignition OFF.
2. Install jumper harness J 44152 to the engine side of the AT inline 20-way connector. Connect a scan tool.
3. Ignition ON. Engine OFF.
4. Using the J 35616 GM terminal test kit, verify that a test lamp illuminates between the ignition 1 voltage circuit, jumper harness terminal E and a good ground.

• If the test lamp does not illuminate, test the ignition 1 voltage circuit for an open/high resistance or short to ground. If all circuits and connections test normal, replace the TCM.

• If test light illuminates.

5. Using the J 35616 GM terminal test kit, connect a test lamp between the ignition 1 voltage circuit, jumper harness terminal E and the 2-3 Shift Solenoid Valve Control circuit, jumper harness terminal B.
6. Using the scan tool special functions, command the 2-3 Shift Solenoid Valve ON and OFF. The test lamp should illuminate when command OFF and turn OFF when commanded ON.

• If the test lamp is always OFF, test the affected circuits for an open. If all circuits and connections test normal, replace the TCM.
• If the test lamp is always ON, test the 2-3 Shift Solenoid Valve Control circuit for a short to ground. If all circuits and connections test normal, replace the TCM.

• If test light performs as commanded.

7. Go to Circuit/System Testing.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the repair.

* 2-3 Shift Solenoid Valve Replacement (2-3 Shift Solenoid Valve Replacement)
* Wiring Harness Replacement (Service and Repair)
* Control Module References (Programming and Relearning)for TCM replacement, setup, and reprogramming

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