GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Caprice WM 🢒 DTC 🢒 DTC P0815 or P816

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 Descriptor

DTC P0815: Upshift Switch Circuit

DTC P0816: Downshift Switch Circuit

Diagnostic Fault Information

Driver Shift Request

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Tap Upshift Switch

--

--

P0815

Tap Downshift Switch

--

--

P0816

Circuit/System Description

The TAP Shift system allows the driver to manually shift gears by using the Upshift and Downshift positions located on the automatic transmission shift Lever. Pushing the lever to the Upshift position will command an upshift and pushing the lever to the Downshift position will command a downshift. The TAP Shift system is activated when the gear selector is in the manual, M, position and is deactivated in all other positions.

Conditions for Running the DTC

P0815

    • No Tap up/ Tap down DTC P0826.
    • No IMS DTCs P1815, P1820, P1822, P1823, P1825 or P1826.
    • The engine run time is greater than 5 seconds.
    • The time since last gear selector range change is greater than 6 seconds.

P0816

    • No Tap up/ Tap down DTC P0826.
    • No IMS DTCs P1815, P1820, P1822, P1823, P1825 or P1826.
    • The engine run time is greater than 5 seconds.
    • The time since last gear selector range change is greater than 6 seconds.

Conditions for Setting the DTC

P0815

The TCM detects an upshift request for 2 seconds in PARK or for 600 seconds.

P0816

The TCM detects a downshift request for 2 seconds in PARK or for 600 seconds.

Action Taken When the DTC Sets

P0815

The TCM disables TAP Shift operation.

P0816

The TCM disables TAP Shift operation.

Conditions for Clearing the DTC

DTCs P0815 and P0816 are Type C DTCs.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Transmission General Description

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

Transmission Control Module Scan Tool Information

Circuit/System Verification
  1. Ignition ON, transmission shift lever in D (+/-), observe the scan tool Driver Shift Request parameter. The reading should display None.
  2. Observe the scan tool Driver Shift Request parameter while pressing the tap-up and tap-down switch. The reading should change between Upshift and Downshift.
  3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the transmission shift lever.
  2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal A and ground.
    3. ⇒If the test lamp does not illuminate, test the IGN circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  3. Verify the scan tool Driver Shift Request parameter indicates Invalid.
    4. ⇒If other than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  4. Ignition OFF, test for 300-600 ohms between the signal circuit terminal B and ground.
    5. ⇒If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM.
    ⇒If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
  5. If all circuits test normal, test or replace the TCM.

Component Testing
  1. Ignition OFF, disconnect the harness connector at the transmission control.
  2. Test for 8.1-8.4 K ohms between terminals A and B.
    3. ⇒If not within the specified range, replace the transmission control.
  3. Test for 2.6-3.2 K ohms between terminals A and B while pressing the upshift button.
    4. ⇒If not within the specified range, replace the transmission control.
  4. Test for 1.0-1.6 K ohms between terminals A and B while pressing the downshift button.
    5. ⇒If not within the specified range, replace the transmission control.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

    • Replace the AT shift switch. Refer to Transmission Control Replacement.
    • Replace the control solenoid (w/body and TCM) valve assembly. Refer to Control Module References for replacement, setup, and programming.