For 1990-2009 cars

### Circuit Description

The 1-2 shift solenoid valve is located in the control valve body of the transmission. The transmission control module (TCM) selects the required gear by turning the appropriate solenoid ON or OFF, enabling the transmission to shift. Refer to Shift Solenoid Valve State and Gear Ratio .

The TCM provides voltage to the solenoid through high side driver 2 (HSD2). The TCM uses a second driver to control the solenoid ground circuit. The controlled ground driver reports feedback voltage to the TCM. When the TCM commands the 1-2 shift solenoid valve ON, the voltage of the control circuit should be approximately 0 volts. When the TCM commands the 1-2 shift solenoid valve OFF, the voltage of the control circuit should be approximately system voltage.

When the TCM detects a continuous open or short to ground in the 1-2 shift solenoid valve circuit, then DTC P0973 sets. DTC P0973 is a type B DTC.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0973 1-2 Shift Solenoid (SS) Control Circuit Low Voltage

### Conditions for Running the DTC

• | Ignition voltage is between 8-18 volts.

• | The engine speed is between 450-6,800 RPM, for 5 seconds.

• | HSD2 is commanded ON.

### Conditions for Setting the DTC

When the following conditions are present and more than 43 out of 50 samples occur, DTC P0973 is set.

• | The TCM detects an open in the 1-2 shift solenoid valve circuit when HSD2 is commanded ON.

• | The TCM detects a short to ground in the 1-2 shift solenoid valve circuit when HSD2 is commanded OFF.

### Action Taken When the DTC Sets

• | Powertrain braking is disabled at the time that the TCM first detects the failure, before the DTC sets.

• | The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL) during the second consecutive drive trip in which the Conditions for Setting the DTC are met.

• | The TCM turns off power to all solenoids.

• | The transmission will operate in fifth gear if the vehicle has successfully completed a 1-2 upshift in the current ignition cycle. If the vehicle has not completed a 1-2 upshift in the current ignition cycle, the transmission will operate in fourth gear.

• | The TCM commands maximum line pressure.

• | The TCM freezes transmission adaptive functions.

• | Torque management is inhibited.

• | At the time of the first failure, the TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.

• | At the time of the second failure, the TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.

• | The TCM stores DTC P0973 in TCM history.

### Conditions for Clearing the DTC

• | The ECM turns OFF the MIL after the sixth consecutive drive trip in which the TCM does not send a MIL illumination request.

• | A scan tool can clear the MIL/clearing DTC.

• | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring.

• | The TCM cancels the default actions when the ignition is OFF long enough in order to power down the TCM.

### Test Description

The number below refers to the step number on the diagnostic table.

1. Listen for an audible click when the solenoid energizes.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.

Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from both the ECM and the TCM.

3. Record the DTC Freeze Frame and Failure Records.
4. Clear the DTC.

Is DTC P0976, P0979 or P2764 also set?

--

Go to Step 3

Go to Step 5

3 | Test the ignition 1 voltage circuit of the 1-2 SS valve for an open or a short to ground between the TCM connector and the AT inline 20-way connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 4
4 | Important: The condition that affects this circuit may exist in other connecting branches of the circuit. Refer to Power Distribution Schematics for complete circuit distribution. Test the ignition 1 voltage circuit of the 1-2 SS valve for an open or a short to ground between the AT inline 20-way connector and the 1-2 SS valve. Refer to Circuit Testing .

Did you find the condition?

--

Go to Step 16

--

5 |

1. Use the scan tool in order to command the 1-2 SS valve ON and OFF 3 times.
2. Listen at the transmission bottom pan.

Does the solenoid click when commanded ON and OFF?

--

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 6

6 |

1. Turn OFF the ignition.
2. Disconnect the AT inline 20-way connector. Additional DTCs may set.
3. Install the J 45681 jumper harness on the engine side of the AT inline 20-way connector.
4. Using the J 35616 GM terminal test kit, connect a test lamp between the ignition 1 voltage and the 1-2 SS valve control circuits of the J 45681 . Refer to Automatic Transmission Inline 20-Way Connector End View .
5. Turn ON the ignition, with the engine OFF.
6. Command the 1-2 SS valve ON and OFF three times.

Is the test lamp ON when you command the solenoid ON, and OFF when you command the solenoid OFF?

--

Go to Step 10

Go to Step 7

7 | Is the test lamp always ON? | -- | Go to Step 8 | Go to Step 9
8 | Test the control circuit of the 1-2 SS valve for a short to ground between the TCM connector and the AT inline 20-way connector. Refer to Testing for Short to Ground and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18
9 | Test the control circuit of the 1-2 SS valve for an open between the TCM connector and the AT inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18
10 |

1. Turn OFF the ignition.
2. Disconnect the J 45681 from the engine side of the AT inline 20-way connector.
3. Install the J 45681 on the transmission side of the AT inline 20-way connector.
4. Using the DMM and the J 35616 GM terminal test kit, measure the resistance between the ignition 1 voltage and the 1-2 SS valve control circuits of the J 45681 . Refer to Automatic Transmission Inline 20-Way Connector End View .

Is the resistance within the specified range?

19-31 Ω

Go to Step 13

Go to Step 11

11 | Is the resistance greater than the specified value? | 31 Ω | Go to Step 12 | Go to Step 13
12 |

1. Test the control circuit of the 1-2 SS valve for an open between the AT inline 20-way connector and the 1-2 SS valve.
2. Test the ignition 1 voltage circuit of the 1-2 SS valve for an open between the AT inline 20-way connector and the 1-2 SS valve.

Refer to Testing for Continuity .

Did you find a condition?

--

Go to Step 16

Go to Step 17

13 | Measure the resistance from the 1-2 SS valve control circuits of the J 45681 to ground. Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance less than the specified value? | 100 Ω | Go to Step 14 | Go to Step 15
14 | Test the control circuit of the 1-2 SS valve for a short to ground between the AT inline 20-way connector and the 1-2 SS valve. Refer to Testing for Short to Ground . Did you find the condition? | -- | Go to Step 16 | --
15 | Measure the resistance between the 1-2 SS valve control circuits and all other terminals, except the 2-3 SS valve control circuit, the TCC PWM solenoid valve control circuit, and the ignition 1 voltage circuit of the J 45681 . Refer to Automatic Transmission Inline 20-Way Connector End View .

Is the resistance less than the specified value?

100 Ω

Go to Step 16

Go to Step 17

16 | Replace the automatic transmission wiring harness. Refer to Transmission Internal Electrical Harness Replacement . Did you complete the replacement? | -- | Go to Step 19 | --
17 | Replace the 1-2 SS valve. Refer to 1-2 Shift Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 19 | --
18 | Replace the TCM. Refer to Control Module References for replacement, setup and programming. Did you complete the replacement? | -- | Go to Step 19 | --
19 | Perform the following procedure in order to verify the repair:

1. Select DTC.
2. Select Clear Info.
3. Operate the vehicle under the following conditions:

• | Drive the vehicle in D.

• | Allow the transmission to obtain a 1-2 upshift.

4. Select Specific DTC.
5. Enter DTC P0973.

Has the test run and passed?

--

Go to Step 20

Go to Step 2

20 | With the scan tool, observe the stored information, capture info. and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK