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 short to voltage in the shift PC solenoid valve circuit, then DTC P0971 sets. DTC P0971 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0971 Shift Pressure Control (PC) Solenoid Control Circuit High 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 short to voltage for 2 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. 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 PCM records the operating conditions when the Conditions 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 P0971 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. |
| • | The TCM clears the MIL when the condition no longer exists for 3 ignition cycles. |
| • | 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 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 in Vehicle DTC Information? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||
Important:
Does the Shift PC Sol. Actual Current reading vary from the Shift PC Sol. Ref. Current reading by more than the specified amount? | 0.10 amps | Go to Step 3 | Go to Intermittent Conditions in Engine Controls - 3.4L | |||||
Does the resistance measure less than the specified value? | 3.8 ohms | Go to Step 4 | Go to Step 5 | |||||
4 | Test the high control circuit of the shift PC solenoid valve and the low control circuit of the shift PC solenoid valve for being shorted together between the AT inline 14-way connector and the PC solenoid. Refer to Circuit Testing in Wiring Systems. Did you find the condition? | -- | Go to Step 7 | Go to Step 8 | ||||
5 | Measure the resistance between the low control circuit of the shift PC solenoid valve and all other circuits, except the high control circuit of the shift PC solenoid valve the transmission side of the AT inline 14-way connector. Refer to Circuit Testing in Wiring Systems. Does the resistance measure less than the specified value? | 100 ohms | Go to Step 7 | Go to Step 6 | ||||
6 | Test the high control circuit and the low control circuit of the shift PC solenoid valve for a short to voltage or a short together between the AT inline 14-way connector and the TCM. Refer to Circuit Testing in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 9 | ||||
7 | Repair or replace the internal automatic transmission wiring harness assembly (33). Refer to Wiring Harness Removal in Unit Repair and Wiring Repairs in Wiring Systems. Did you complete the replacement? | -- | Go to Step 10 | -- | ||||
8 | Replace the control valve body assembly (39). Refer to Control Valve Body Replacement . Is the replacement complete? | -- | Go to Step 11 | -- | ||||
9 | Replace the TCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Is the replacement complete? | -- | Go to Step 11 | -- | ||||
10 | Perform the following procedure in order to verify the repair:
Does the DTC reset? | -- | Go to Step 2 | Go to Step 11 | ||||
11 | 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 in Vehicle DTC Information | System OK |
