6T30/6T40/6T45 - Automatic Transmission
DTC P0815, P0816, or P0826
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (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
Typical Scan Tool Data
Circuit/System Description
When the shift lever is placed in manual mode (M), the driver shift request (DSR), also known as the tap shift function, is activated. The DSR allows the vehicle operator to shift gears by pressing the plus (+) button for an upshift or the minus (-) button for a downshift. The body control module (BCM) provides ignition voltage to the resistor array in the switch. When a plus or minus button is pressed, there is a corresponding change in the resistance, resulting in change to the voltage drop. The change in voltage on the signal circuit is monitored by the transmission control module (TCM). The TCM commands the upshift or downshift, providing the operating conditions are correct for the shift.
Conditions for Running the DTC
P0815 or P0816
* The engine speed is greater than 500 RPM for at least 5 seconds.
* The ignition voltage is between 9.0 volts and 18.0 volts.
* No DTCs P0816, P0826, P1761 or P182E.
P0826
* The engine speed is greater than 500 RPM for at least 5 seconds.
* The ignition voltage is between 9.0 volts and 18.0 volts.
* No DTCs P0826 or P1761.
Conditions for Setting the DTC
P0815 - Condition 1
The TCM detects an upshift request for 1 second or greater in PARK or NEUTRAL.
Condition 2
The TCM detects an upshift request for 600 seconds with the transmission in a forward range.
P0816 - Condition 1
The TCM detects a downshift request for 1 second in PARK or NEUTRAL.
Condition 2
The TCM detects a downshift request for 600 seconds with the transmission in a forward range.
P0826
The TCM detects an invalid voltage on the TAP up/down signal circuit for 60 seconds or greater.
Action Taken When the DTC Sets
* DTCs P0815, P0816, and P0826 are Type C DTCs.
* The TCM disables TAP shift operation.
Conditions for Clearing the DTC
DTCs P0815, P0816, and P0826 are Type C DTCs.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (6T30/6T40/6T45 - Automatic Transmission)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
* Transmission General Description (Transmission General Description)
* Transmission Component and System Description (Transmission Component and System Description)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. If other DTCs are set, diagnose them first.
2. Ignition ON, transmission shift lever in Park, observe the scan tool Driver Shift Control parameter. The reading should display Inactive.
3. With the transmission shift lever in manual mode (M), observe the scan tool Driver Shift Control parameter. The reading should display active.
4. Press the left Tap Up (+) switch, left Tap Down (-) switch, right Tap Up (+) switch and right Tap Down (-) switch while observing the scan tool Up and Down Shift Switch parameter. The parameter should read Upshift when the Tap Up switch is pressed, and Downshift when the Tap Down switch is pressed, and None when neither switch is pressed.
5. 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 left automatic transmission manual shift switch connector.
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 3 and ground.
• If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
3. Ignition OFF, test for 8.0-8.5 k ohms between the left automatic transmission manual shift switch terminals 3 and 5. Verify the resistance changes to 2.7-3.1 k ohms when the Tap Up switch is pressed and 1.1-1.5 k ohms when the Tap Down switch is pressed.
• If not the specified value, replace the left automatic transmission manual shift switch.
4. Test for open circuit on the left automatic transmission manual shift switch harness connector between terminals 1 and 2 and between terminals 2 and 3. Test for less than 10 ohms between terminals 1 and 2 when the right automatic transmission manual shift tap down (-) switch is pressed and between terminals 2 and 3 when the Tap Up (+) switch is pressed.
• If not the expected results, test the circuits between the left and right automatic transmission manual shift switch for an open/high resistance or short to ground. If circuits test normal, replace the right automatic transmission manual shift switch.
5. Test the Tap Up/Tap Down signal circuit for an open/high resistance or short to ground.
• If circuit tests normal, replace the control solenoid valve assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Replacement (Service and Repair).
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Refer to Control Module References (Programming and Relearning) for BCM replacement, setup, and programming.