GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 HUMMER 🢒 2008 🢒 H2 🢒 Transmission/Transaxle 🢒 Automatic Transmission - 6L50/6L80/6L90 🢒 DTC P0815, P0816, or P0826

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0815:  Upshift Switch Circuit

DTC P0816:  Downshift Switch Circuit

DTC P0826:  Up and Down Shift Switch Circuit

Diagnostic Fault Information

Driver Shift Control

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Tap Up/Tap Down Switch Signal Circuit

0 V

0 V

5-12 V

--

Circuit/System Description

The driver shift control (DSC), also known as the TAP shift, allows the driver to manually shift by pressing the steering wheel mounted Plus (+) or Minus (-) switches to select the desired gear for current driving conditions. Pushing the Plus (+) switch will command an upshift and pushing the Minus (-) switch will command a downshift. The DSC is powered by 12 volts which begins at the body control module (BCM), through the DSC switch resistor array and back to the BCM. The DSC system is activated when the gear selector is in the Manual Mode (M) position. The DSC system is Inactive in all other range positions, and when the Tow/Haul or Cruise Control features are in use.

Conditions for Running the DTC

P0815 or P0816

    • No DTC P0826.
    • No DTCs P1825 or P1915.
    • The engine speed is between 500-7,500 RPM for at least 5 seconds.
    • The time since the last gear selector range change is greater than 6 seconds.
    • The DSC is powered by 12 volts.

P0826

    • Engine speed is 500-6,500 RPM for at least 5 seconds.
    • Ignition voltage is 8.6-19.0 volts.
    • The DSC is powered by 12 volts.

Conditions for Setting the DTC

P0815

The BCM detects a stuck On upshift switch (+) for 3 seconds in PARK, REVERSE, NEUTRAL, or D6 and for 600 seconds in PARK, REVERSE, NEUTRAL, D2, D4, or D6.

P0816

The BCM detects a stuck On downshift switch (-) for 3 seconds in PARK, REVERSE, NEUTRAL, or D6 and for 600 seconds in PARK, REVERSE, NEUTRAL, D2, D4, or D6.

P0826

The BCM detects an invalid voltage on the DSC upshift/downshift signal circuit for 8 seconds.

Action Taken When the DTC Sets
    • DTCs P0815, P0816, and P0826 are Type C DTCs.
    • The BCM disables DSC shift operation.

Conditions for Clearing the DTC

DTCs P0815, P0816, and P0826 are Type C DTCs.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

P0815, P0816, or P0826

With the engine ON, engage the DSC Plus/Minus switch positions while observing the Driver Shift Request parameter in the transmission scan tool data list. The parameter should change to reflect the selected Upshift or Downshift switch position. With no Upshift or Downshift switch position selected, the parameter should display Inactive.

Circuit/System Testing

P0815

  1. Select the Driver Shift Request parameter from the transmission data list.
  2. Disconnect the automatic transmission DSC switch connector below the steering column.
    3. ⇒If the parameter status changes from Upshift to Invalid, replace the DSC switch.
    ⇒If the parameter status does not change, replace the BCM.

P0816

  1. Select the Driver Shift Request parameter from the transmission data list.
  2. Disconnect the DSC switch connector below the steering column.
    3. ⇒If the parameter status changes from Downshift to Invalid, replace the DSC switch.
    ⇒If the parameter status does not change, replace the BCM.

P0826

  1. Test the 12-volt circuit and the up and down switch signal circuit for a short to ground.
    2. ⇒If the circuits test OK, test the 12-volt circuit and the up and down signal circuit for an open or short to voltage.
  2. Test the DSC switch for correct resistance value, 8.11-8.39 ohms.
    3. ⇒If the resistance is not within specifications, replace the DSC switch assembly.
    ⇒If the resistance is within specifications, replace the BCM.

Component Testing

Test the DSC switch for correct resistance value, 8.11-8.39 ohms.

⇒If the resistance is not within specifications, replace the DSC switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    • Replace the DSC switch. Refer to Steering Wheel Replacement.
    • Replace the BCM. Refer to Control Module References for replacement, setup, and programming.