Buick Regal: DTC P0815, P0816, or P0826

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 P0815

Upshift Switch Circuit

DTC P0816

Downshift Switch Circuit

DTC P0826

Up and Down Shift Switch Circuit

Diagnostic Fault Information

Typical Scan Tool Data

Driver Shift Request

Circuit/System Description

The switch S2 has an internal resistor ladder network. A specific resistance is generated dependent on the position of the switch.

Conditions for Running the DTC

• Ignition Voltage=9 to 32 V
• K71 Transmission Control Module= Communication Enabled
• K9 Body Control Module= Communication Enabled

Frequency the DTC runs=Continuously - After the running conditions are met - For 2 s

Conditions for Setting the DTC

P0815Condition 1

• Transmission Range=Park/Neutral/Reverse
• Driver Shift Request=Upshift

The above conditions must occur for greater than 2 s.

Condition 2

• Transmission Range=Drive
• Driver Shift Request=Upshift

The above conditions must occur for greater than 29 s.

P0816Condition 1

• Transmission Range=Park/Neutral/Reverse
• Driver Shift Request=Downshift

The above conditions must occur for greater than 2 s.

Condition 2

• Transmission Range=Drive
• Driver Shift Request=Downshift

The above conditions must occur for greater than 29 s.

P0826

Driver Shift Request=Illegal Mode

Actions Taken When the DTC Sets

DTCs P0815, P0816, P0826 are Type C DTCs.

Manual Shift Control=Disabled

Conditions for Clearing the DTC

DTCs P0815, P0816, P0826 are Type C DTCs.

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

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 - On / Vehicle - In Service Mode

2. Verify the scan tool parameter:Driver Shift Request=Inactive

• If not the specified state

Refer to Circuit/System Testing

• Go to next step: If the specified state

3. Operate the component:S2 Transmission Manual Shift Switch

Verify the scan tool parameter:Driver Shift Request=Upshift/Downshift

• If not the specified state

Refer to Circuit/System Testing

• Go to next step: If the specified state

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.

2. Disconnect the electrical connector:S3 Transmission Shift Lever.

3. Test for less than 10 ohms between the test points:Ground circuit terminal 2@S3 Transmission Shift Lever (harness side) & Ground.

• If 10 ohms or greater

1. Disconnect the ground connection:G305
2. Test for less than 2 ohms between the test points:Ground circuit terminal 2@S3 Transmission Shift Lever (harness side) & G305
   • If 2 ohms or greater - Repair the open/high resistance in the circuit.
   • If less than 2 ohms - Repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 ohms

4. Ignition - On / Vehicle - In Service Mode.

5. Test for greater than 10 V between the test points:Signal circuit terminal 3@S3 Transmission Shift Lever & Ground.

• If 10 V or less

1. Ignition/Vehicle - Off
2. Disconnect the electrical connector:K9 Body Control Module
3. Test for infinite resistance between the test points:Signal circuit terminal 3@S3 Transmission Shift Lever (harness side) & Ground
   • If less than infinite resistance - Repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
4. Test for less than 2 ohms between the test points:Signal circuit terminal 3@S3 Transmission Shift Lever (harness side) & The other end of the circuit@K9 Body Control Module (harness side)
   • If 2 ohms or greater - Repair the open/high resistance in the circuit.
   • If less than 2 ohms - Replace the component:K9 Body Control Module

• If greater than 10 V

6. Test or replace the component:S2 Transmission Manual Shift Switch.

Component Testing

1. Ignition/Vehicle - Off.

2. Disconnect the electrical connector:S3 Transmission Shift Lever.

3. Test the resistance between the test points:Signal terminal 3 & Ground terminal 2.

Operate the component:S2 Transmission Manual Shift Switch

• Switch - Not Pressed=5300 to 5800 ohms
• Switch - Pressed - Upshift=600 to 660 ohms
• Switch - Pressed - Downshift=1900 to 2100 ohms
• If not the specified values

Replace the component:S3 Transmission Shift Lever

• Go to next step: If the specified values

4. All OK.

Repair Instructions

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

• Refer to Transmission Control Lever Knob Replacement - S3 Transmission Shift Lever
• For control module replacement, programming, and setup: Refer to Control Module: References

DTC P086F

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:Strategy Based Diagnosis
• An overview of each diagnostic category can be found here: Refer to Diagnostic Procedure Instructions

DTC Descriptor

DTC P086F

Neutral Position Not Learned

Circuit/System Description

If the learned position is not stored in the control module K71, DTC P086F sets.

Conditions for Running the DTC

• DTC P0603 = Not set
• Ignition=On

DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

Neutral Position=Not Learned

Actions Taken When the DTC Sets

• DTC P086F is a Type C DTC.
• Engine Cranking=Disabled

Conditions for Clearing the DTC

DTC P086F is a Type C DTC.

Reference Information

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 learn/reset function: Refer to Gear Selector -N- Position Learn.

3. Verify the DTC does not set.

• If the DTC sets

Replace the component:K71 Transmission Control Module

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

4. All OK.

Repair Instructions

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

For control module replacement, programming, and setup: Refer to Control Module: References

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