Buick Regal: DTC P0778, P0966, or P0967

Diagnostic Instructions

• Perform the Diagnostic System Check prior to using this diagnostic procedure: Refer to Diagnostic System Check - Vehicle
• Review the description of Strategy Based Diagnosis: Refer to Strategy Based Diagnosis
• An overview of each diagnostic category can be found here: Refer to Diagnostic Procedure Instructions

DTC Descriptor

DTC P0778

Pressure Control Solenoid Valve 2 Control Circuit

DTC P0966

Pressure Control Solenoid Valve 2 Control Circuit Low Voltage

DTC P0967

Pressure Control Solenoid Valve 2 Control Circuit High Voltage

Diagnostic Fault Information

Typical Scan Tool Data

Pressure Control Solenoid Valve 2 Control Circuit High Voltage Test Status

Pressure Control Solenoid Valve 2 Control Circuit Low Voltage Test Status

Pressure Control Solenoid Valve 2 Control Circuit Open Test Status

Circuit/System Description

The solenoid valve controls the flow of transmission fluid to the hydraulic actuator that controls the C2 clutch.

Conditions for Running the DTC

• { P0778 }DTC P0606, P0657, P0962, P0963, P0966, P0967, P0970, P0971, P2720, P2721, P2729, P2730, P2738, P2739 = Not set
• { P0966 }DTC P0606, P0657, P0963, P0967, P0971, P2721, P2730, P2739 = Not set
• { P0967 }DTC P0606, P0657, P0962, P0966, P0970, P2720, P2729, P2738, = Not set
• Ignition Voltage=9 to 32 V

Frequency the DTC runs=Continuously - After the running conditions are met

Conditions for Setting the DTC

P0778

Control Circuit=Commanded state does not match the actual state

P0966

Control Circuit=Less than 20 mA - For greater than 1 s

P0967

Control Circuit=Greater than 1358 mA - For greater than 1 s

Actions Taken When the DTC Sets

DTCs listed in the DTC Descriptor Category=Type A DTC

• Fail-Safe Mode=Active
• Learning=Disabled
• Transmission gear allowed=3rd Gear - After a stop

Conditions for Clearing the DTC

DTCs listed in the DTC Descriptor Category=Type A DTC

Reference Information

Schematic: Reference

Refer to Automatic Transmission Controls Wiring Schematics.

Connector End View: Reference

Refer to Component Connector End View Index.

Component View: Reference

Refer to Disassembled Views.

Description and Operation

Refer to Transmission General Description.

Electrical Information: Reference

• Refer to Circuit Testing
• Refer to Connector Repairs
• Refer to Testing for Intermittent Conditions and Poor Connections
• Refer to Wiring Repairs

DTC Type: Reference

Refer to Powertrain Diagnostic Trouble Code (DTC) Type Definitions.

Scan Tool: Reference

Refer to Control Module: References.

Circuit/System Verification

1. Ignition - On / Vehicle - In Service Mode

2. Perform the scan tool control function:Pressure Control Solenoid Valve 2 - Enable & Disable

Verify the scan tool parameter:

• Pressure Control Solenoid Valve 2 Control Circuit High Voltage Test Status=Not Run or OK
• Pressure Control Solenoid Valve 2 Control Circuit Low Voltage Test Status=Not Run or OK
• Pressure Control Solenoid Valve 2 Open Circuit Test Status=Not Run or OK
• If not the specified state

Refer to Circuit/System Testing

• Go to next step: If the specified state

3. Perform the scan tool control function:Pressure Control Solenoid Valve 2 - Increase & Decrease

Verify the component produces a clicking sound:Q27B Pressure Control Solenoid Valve 2

• If the component does not produce a sound

Refer to Circuit/System Testing

• Go to next step: If the component produces a sound

4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Verify the DTC does not set.

• If the DTC sets

Refer to Circuit/System Testing

• Go to next step: If the DTC is not set

5. All OK.

Circuit/System Testing

NOTE: It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

1. Ignition/Vehicle & All vehicle systems - Off

NOTE: Twisting or tilting of the transmission control module electrical connector while disconnecting may result in bent or misaligned electrical terminal pins.

2. Remove the component:K71 Transmission Control Module

NOTE: The component's temperature should be 19 to 21ºC (66 to 70ºF) while testing.

3. Test for 5.0 to 5.6 ohms between the test points:Control circuit terminal 8 & Low: Reference circuit terminal 9

• If not between 5.0 and 5.6 ohms

1. Remove the component:Control Valve Body Cover
2. Disconnect the electrical connector:Q27B Pressure Control Solenoid Valve 2
3. Test for less than 2 ohms between the test points:
   • Control circuit terminal 2@Component harness & Control circuit terminal 8@Control module harness
   • Low: Reference circuit terminal 1@Component harness & Low: Reference circuit terminal 9@Control module harness
   • If 2 ohms or greater - Replace the component:Automatic Transmission Wiring Harness
   • If less than 2 ohms - Replace the component:Q27B Pressure Control Solenoid Valve 2

• Go to next step: If between 5.0 and 5.6 ohms

4. Test for infinite resistance between the test points:

• Control circuit terminal 8 & Transmission Case
• Low: Reference circuit terminal 9 & Transmission Case
• If less than infinite resistance

1. Remove the component:Control Valve Body Cover
2. Disconnect the electrical connector:Q27B Pressure Control Solenoid Valve 2
3. Test for infinite resistance between the test points:
   • Control circuit terminal 2@Component harness & Transmission Case
   • Low: Reference circuit terminal 1@Component harness & Transmission Case
   • If less than infinite resistance - Replace the component:Automatic Transmission Wiring Harness
   • If infinite resistance - Replace the component:Control Valve Body

• Go to next step: If infinite resistance

5. Replace the component:K71 Transmission Control Module

Component Testing

1. Ignition/Vehicle - Off

2. Disconnect the electrical connector:Q27B Pressure Control Solenoid Valve 2

NOTE: The component's temperature should be 19 to 21ºC (66 to 70ºF) while testing.

3. Test for 5.0 to 5.6 ohms between the test points:Control terminal 2 & Low: Reference terminal 1

• If not between 5.0 and 5.6 ohms

Replace the component:Control Valve Body

• Go to next step: If between 5.0 and 5.6 ohms

4. Test for infinite resistance between the test points:Each terminal of the component & The component's housing

• If less than infinite resistance

Replace the component:Control Valve Body

• Go to next step: If infinite resistance

5. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair: Refer to Diagnostic Repair Verification

• Refer to Control Valve Body Replacement
• Refer to Wiring Harness Wire Replacement
• For control module replacement, programming, and setup: Refer to Control Module: References

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