Circuit Description
The 1-2 shift solenoid (1-2 SS) valve controls transmission fluid pressure acting on the 1-2 shift valves to position the valves for the appropriate gear. The 1-2 SS valve is a normally-open exhaust valve located on the control valve body. A fused circuit supplies ignition voltage to the 1-2 SS valve. The transmission control module (TCM) commands the solenoid ON or OFF by switching the ground path. When the 1-2 SS valve is commanded ON, the TCM senses low voltage. When the 1-2 SS valve is commanded OFF, the TCM senses high voltage. Refer to Shift Solenoid Valve State and Gear Ratio .
If the TCM detects a continuous open or short to ground in the 1-2 SS 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
The ignition is ON.
Conditions for Setting the DTC
The TCM detects an open or short to ground in the 1-2 SS valve control circuit for 4.4 seconds.
Action Taken When the DTC Sets
| • | The TCM requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. |
| • | The TCM commands maximum line pressure. |
| • | The TCM freezes transmission adaptive function. |
| • | The TCM commands an alternate coast shift pattern where downshifts occur at higher vehicle speeds while coasting. |
| • | The TCM inhibits 3-2 downshifts when the vehicle speed is greater than 52 km/h (32 mph). |
| • | The TCM disables the touch activated power (TAP) shift operation. |
| • | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Freeze Frame and Failure Records. |
| • | The TCM stores DTC P0973 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met. |
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after the third consecutive trip in which the TCM does not send an MIL illumination request. |
| • | A scan tool can clear the MIL/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 DTC default actions when the ignition switch is OFF long enough in order to power down the TCM. |
Diagnostic Aids
| • | Ensure the wiring harness is not stretched too tightly or other components are pressing on the automatic transmission inline 20-way connector body. |
| • | Inspect for proper clearance to all other components and wiring. Refer to Testing for Intermittent Conditions and Poor Connections . |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. Using the Clear Info function will erase the stored Freeze Frame and Failure Records from the TCM. Are DTC P0976 or P2764 also set? | -- | Go to Step 3 | Go to Step 9 | |
3 |
Is the fuse open? | -- | Go to Step 4 | Go to Step 7 |
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 a short to ground between the fuse block and the automatic transmission inline 20-way connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 5 |
5 |
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. Did you find the condition? | -- | Go to Step 17 | Go to Step 6 |
6 |
Did you complete the replacement? | -- | Go to Step 20 | -- |
7 | Test the ignition 1 voltage circuit of the 1-2 SS valve for an open between the fuse block and the automatic transmission inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 8 |
8 | Test the ignition 1 voltage circuit of the 1-2 SS valve for an open between the automatic transmission inline 20-way connector and the solenoid. Refer to Testing for Continuity . Did you find the condition? | -- | Go to Step 17 | Go to Testing for Intermittent Conditions and Poor Connections |
9 |
Does the test lamp turn ON and OFF? | -- | Go to Step 12 | Go to Step 10 |
10 | Test the ignition 1 voltage circuit of the 1-2 SS valve for an open between the fuse block and the automatic transmission inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 11 |
11 | Test the control circuit of the 1-2 SS valve for an open or short to ground between the TCM and the automatic transmission inline 20-way connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 19 |
12 |
Does the resistance measure within the specified range? | 19-31 ohms | Go to Step 13 | Go to Step 16 |
13 | Measure the resistance from both terminals of the 1-2 SS valve to the transmission case. Are both readings greater than the specified value? | 250 K ohms | Go to Step 14 | Go to Step 15 |
14 | Measure the resistance on the control side of the 1-2 SS valve and all other terminals of the automatic transmission inline 20-way connector. Refer to Testing for Continuity . Is the resistance less than the specified value? | 250 K ohms | Go to Step 16 | Go to Testing for Intermittent Conditions and Poor Connections |
15 |
Are both readings greater than the specified value? | 250 K ohms | Go to Step 17 | Go to Step 18 |
16 |
Is the resistance within the specified range? | 19-31 ohms | Go to Step 17 | Go to Step 18 |
17 | Replace the automatic transmission wiring harness assembly. Refer to Wiring Harness Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- |
18 | Replace the 1-2 SS valve. Refer to 1-2 Shift Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- |
19 | Replace the TCM. Refer to Control Module References for replacement, setup and programming. Did you complete the replacement? | -- | Go to Step 20 | -- |
20 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | First: 2.87:1-2.97:1 Second: 1.52:1-1.62:1 Third: 0.95:1-1.05:1 Fourth: 0.65:1-0.75:1 | Go to Step 21 | Go to Step 2 |
21 | With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
