Circuit Description
The shift pressure control (PC) solenoid valve regulates solenoid modulator fluid passing through the solenoid into shift control pressure. The TCM uses a pulse width modulated signal in order to control the signal pressure. The TCM compares various inputs in order to determine the appropriate pressure for a given load. The TCM varies the current to the shift PC solenoid valve from 0.1 amps, for maximum line pressure to 1.1 amps, for minimum line pressure. An internal current monitor within the TCM provides feedback in order to determine actual shift PC solenoid valve current draw.
If the TCM detects a continuous open or short to ground in the shift PC solenoid valve circuit, then DTC P0970 sets. DTC P0970 is a type A DTC.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
The shift PC solenoid valve feedback circuit indicates a continuous open or short to ground for 12.5 seconds or greater.
Action Taken When the DTC Sets
| • | The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL). |
| • | The TCM turns the Trans. Protection Mode ON. When the Trans. Protection Mode is ON, the following conditions occur: |
| - | The transmission will operate in 5th gear when the transmission is shifted into D or I range and 2nd gear when shifted into L range. |
| - | The line pressure is at maximum. |
| - | The torque converter clutch (TCC) is disabled. |
| - | The TCM freezes the transmission adaptive functions. |
| • | 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 P0970 in TCM history. |
Conditions for Clearing the MIL/DTC
| • | The ECM turns off the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | A scan tool can clear the 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 is OFF long enough in order to power down the TCM. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies the ability of the TCM to command the shift PC solenoid valve.
-
This step verifies that the automatic transmission wiring harness and the shift PC solenoid valve have correct resistance.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls - 3.0L (L81) | ||||
Important:
Does the Shift PC Sol. Actual Current reading vary from the Shift PC Sol. Ref. Current reading by more than the specified amount? | 0.05 amps | Go to Step 3 | Go to Intermittent Conditions in Engine Controls - 3.0L (L81) | |||||
Is the resistance within the specified range? | 3.8-8.3 ohms | Go to Step 7 | Go to Step 4 | |||||
4 | Is the resistance greater than the specified value? | 8.3 ohms | Go to Step 5 | Go to Step 6 | ||||
5 |
Refer to Testing for Continuity in Wiring Systems. Did you find a condition? | -- | Go to Step 18 | Go to Step 19 | ||||
6 | Test the high control circuit (CKT 2880) and the low control circuit (CKT 5508) of the shift PC solenoid valve for being shorted together between the AT inline 14-way connector and the shift PC solenoid valve. Refer to Testing for Continuity in Wiring Systems. Did you find the condition? | -- | Go to Step 18 | Go to Step 19 | ||||
7 | Measure the resistance from terminal 9 of the transmission side of the AT inline 14-way connector to ground. Is the resistance less than the specified value? | 10 ohms | Go to Step 8 | Go to Step 9 | ||||
8 |
Refer to Testing for Short to Ground in Wiring Systems. Did you find a condition? | -- | Go to Step 18 | Go to Step 19 | ||||
9 | Measure the resistance between terminal 9 and all other terminals, except terminal 2, of the transmission side of the AT inline 14-way connector. Is the resistance between terminal 9 and any other terminal, except terminal 2, less than the specified value? | 100 ohms | Go to Step 18 | Go to Step 10 | ||||
10 |
Is the resistance less than the specified value? | 10 ohms | Go to Step 11 | Go to Step 12 | ||||
11 | Test the low control circuit (CKT 1229) of the shift PC solenoid for a short to ground between the TCM connector and the AT inline 14-way connector. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | -- | ||||
12 | Using the DMM and the J-35616 GM-approved terminal test kit, measure the resistance between terminal 2 of the harness side of the AT inline 14-way connector and terminal 36 of the TCM C2 connector. Is the resistance less than the specified value? | 10 ohms | Go to Step 14 | Go to Step 13 | ||||
13 | Test the low control circuit (CKT 5508) of the shift PC solenoid valve for an open between the TCM connector and the AT inline 14-way connector. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | -- | ||||
14 | Using the DMM and the J-35616 GM-approved terminal test kit, measure the resistance from terminal 9 of the harness side of the AT inline 14-way connector to ground. Is the resistance less than the specified value? | 10 ohms | Go to Step 15 | Go to Step 16 | ||||
15 | Test the high control circuit (CKT 2880) of the shift PC solenoid valve for a short to ground between the TCM connector and the AT inline 14-way connector. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | -- | ||||
16 | Using the DMM and the J-35616 GM-approved terminal test kit, measure the resistance between terminal 9 of the harness side of the AT inline 14-way connector and terminal 26 of the TCM connector. Is the resistance less than the specified value? | 10 ohms | Go to Step 20 | Go to Step 17 | ||||
17 | Test the high control circuit (CKT 2880) of the shift PC solenoid valve for an open between the TCM connector and the AT inline 14-way connector. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | -- | ||||
18 | Replace the automatic transmission wiring harness. Refer to Wiring Harness Removal . Is the action complete? | -- | Go to Step 21 | -- | ||||
19 | Replace the control valve body assembly. Refer to Control Valve Body Replacement . Is the action complete? | -- | Go to Step 21 | -- | ||||
20 | Replace the TCM. Refer to Transmission Control Module Replacement . Is the action complete? | -- | Go to Step 21 | -- | ||||
21 | Perform the following procedure in order to verify the repair:
Does the DTC reset? | -- | Go to Step 2 | Go to Step 22 | ||||
22 | 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 in Engine Controls - 3.0L (L81) | System OK |
