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 CircuitDTC P0816: Downshift Switch Circuit
DTC P0826: Up and Down Shift Switch Circuit
Diagnostic Fault Information
Driver Shift Request
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 transmission modes and gears by pressing the Plus/Minus button and select the desired range of gears for your current driving conditions by using the DSC shift switch located on the automatic transmission gear shift lever. Pushing the Plus switch will command an upshift and pushing the Minus switch will command a downshift. 12 volt reference voltage flows from the ignition body control module (BCM) through the DSC switch resistor array to the BCM. The DSC shift system is activated when the gear selector is in the Manual (M) position. DSC system is deactivated in all other range positions.
Conditions for Running the DTC
| • | The engine speed is between 500-6,500 RPM for at least 5 seconds. |
| • | No DTC P0826. |
| • | The vehicle speed is less than 200 km/h (124 mph) for 5 seconds. |
| • | The transmission fluid temperature (TFT) is -59 to +159°C (-74 to +318°F). |
| • | The system voltage is 11-18 volts. |
Conditions for Setting the DTC
P0815
The BCM detects an upshift request for 3 seconds when the transmission range selector is in D or 600 seconds in P, R, or N.
P0816
The BCM detects a downshift request for 3 seconds when the transmission range selector is in D or 600 seconds in P, R, or N.
P0826
The BCM detects an invalid voltage on the TAP up/down signal circuit for 5 seconds.
Action Taken When the DTC Sets
| • | P0815, P0816, and P0826 are Type C DTCs. |
| • | The BCM disables TAP shift operation. |
Conditions for Clearing the DTC
P0815, P0816, and P0826 are Type B DTCs.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
Electrical Information Reference
| • | Circuit Testing |
| • | 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 body controls scan tool data list. The parameter should change to reflect the selected Up or Downshift switch position and with no Up or Downshift switch position selected the parameter should display None.
Circuit/System Testing
P0815
- Select the Driver Shift Request parameter.
- Disconnect the automatic transmission DSC shift switch connector.
| ⇒ | If the parameter status changes from Upshift to Invalid, replace the DSC shift switch. |
| ⇒ | If the parameter status does not change, replace the BCM. |
P0816
- Select the Driver Shift Request parameter.
- Disconnect the DSC shift switch connector.
| ⇒ | If the parameter status changes from Downshift to Invalid, replace the DSC shift switch. |
| ⇒ | If the parameter status does not change, replace the BCM. |
P0826
- Test the 12 volt reference circuit and the tap up and tap down switch signal circuit for a short to ground.
- Test the DSC shift switch for correct resistance value, 8.11-8.39 ohms.
| ⇒ | If the circuits test OK, test the 12 volt reference circuit and the tap up and tap down signal circuit for an open or short to voltage. |
| ⇒ | If the resistance is not within specifications, replace the switch assembly. |
| ⇒ | If the resistance is within specifications, replace the BCM. |
Component Testing
Test the DSC shift 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.
| • | Shift Lever Replacement for DSC shift switch replacement. |
| • | Control Module References for BCM replacement, setup, and programming. |
