Circuit Description
The shift pressure control (PC) solenoid valve regulates solenoid modulator fluid passing through the solenoid into shift control pressure. The transmission control module (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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0970 Shift Pressure Control (PC) Solenoid Control Circuit Low Voltage
Conditions for Running the DTC
| • | The engine speed is 400 RPM or greater. |
| • | The ignition voltage is 10.2-15.5 volts. |
| • | Trans. protection mode is OFF. |
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 powertrain control module (PCM) to illuminate the malfunction indicator lamp (MIL). |
| • | The TCM turns the Trans. Protection Mode ON. |
| • | The transmission will operate in 4th gear when the transmission is shifted into D. |
| • | The line pressure is at maximum. |
| • | The torque converter clutch (TCC) is disabled. |
| • | The TCM freezes the transmission adaptive functions. |
| • | The TCM disables engine braking. |
| • | The PCM records the operating conditions when the Condition for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records. |
| • | 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 PCM 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 - Vehicle? | -- | Go to Step 2 | |||||
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 amp | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections | |||||
Does the resistance measure 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 . Did you find a condition? | -- | Go to Step 18 | Go to Step 19 | ||||
6 | Test the high control circuit and the low control circuit 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 . 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. Does the resistance measure less than the specified value? | 10 ohms | Go to Step 8 | Go to Step 9 | ||||
8 |
Refer to Testing for Short to Ground . 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. Does the resistance measure less than the specified value? | 100 ohms | Go to Step 18 | Go to Step 10 | ||||
10 |
Does the resistance measure less than the specified value? | 10 ohms | Go to Step 11 | Go to Step 12 | ||||
11 | Test the low control circuit 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 . 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 of the low control circuit of the shift PC solenoid valve between the harness side of the AT inline 14-way connector and the TCM C2 connector. Does the resistance measure less than the specified value? | 10 ohms | Go to Step 14 | Go to Step 13 | ||||
13 | Test the low control circuit 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 . 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 of the high control circuit of the shift PC solenoid valve at the harness side of the AT inline 14-way connector to ground. Does the resistance measure less than the specified value? | 10 ohms | Go to Step 15 | Go to Step 16 | ||||
15 | Test the high control circuit 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 . 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 of the high control circuit of the shift PC solenoid valve between the harness side of the AT inline 14-way connector and the TCM connector. Does the resistance measure less than the specified value? | 10 ohms | Go to Step 20 | Go to Step 17 | ||||
17 | Test the high control circuit 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 . Did you find and correct the condition? | -- | Go to Step 21 | -- | ||||
18 | Replace the automatic transmission wiring harness. Refer to Wiring Harness Removal in the Unit Repair Manual. Did you complete the action? | -- | Go to Step 21 | -- | ||||
19 | Replace the control valve body assembly. Refer to Control Valve Body Replacement . Did you complete the action? | -- | Go to Step 21 | -- | ||||
20 | Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the action? | -- | 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? | -- | System OK |
