6T70/6T75 - 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
Diagnostic Fault Information
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
* No DTCs P0815, P0816, P0826, P1761, P182E, P1876, P1877, or P1915.
* The time since the range change is greater than 1 second.
* The engine speed is 400 RPM or greater for 5 seconds.
* The ignition voltage is 8.6 volts or greater.
P0826
* The engine speed is greater than 400 RPM for at least 5 seconds.
* The ignition voltage is 8.6 volts or greater.
* No DTC 1761.
Conditions for Setting the DTC
P0815 - Condition 1
The TCM detects an upshift request for 1 second in PARK or neutral.
P0815 - Condition 2
The TCM detects an upshift request for 10 minutes in any forward range.
P0816 - Condition 1
* The TCM detects a downshift request for 1 second in PARK or neutral.
* The TCM detects a downshift request for 10 minutes in any forward range.
P0826
The TCM detects an invalid voltage on the TAP up/down signal circuit for 1 minute.
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 Electrical Diagrams
Connector End View Reference
* Component Connector End Views Connector End Views By Name
* Inline Harness Connector End Views Connector Views
Description and Operation
Transmission General Description Transmission General 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 Control Module References 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 Tap Up (+) switch and Tap Down (-) switch while observing the scan tool Driver Shift Request parameter. The parameter should read Upshift when the Tap Up switch is pressed, Downshift when the Tap Down switch is pressed, and None when neither switch is pressed.
5. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions you observe from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, then STOP. Do not perform the Circuit/System Testing or Component Testing as this may result in an unnecessary part replacement. Refer to Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections.
Circuit/System Testing
1. Ignition OFF, disconnect the vehicle harness 6-way connector at the transmission shift lever assembly.
2. Ignition ON, verify that a test lamp illuminates between the vehicle harness connector ignition circuit terminal 1 and ground.
• If the test lamp does not illuminate, test the ignition 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.
• 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 8.0-8.5 k ohms between the automatic transmission shift lever connector terminals 1 and 2. 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, test the circuits between the automatic shift lever assembly connector and shift lever knob connector for a short or an open/high resistance. If the circuits test normal, replace the automatic transmission shift lever knob.
5. Test the Tap Up/Tap Down signal circuit for an open/high resistance or short to ground.
• If the 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
Note:
* Perform the Reset Transmission Adapts Programming and Relearning following all transmission related repairs.
* Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection Component Tests and General Diagnostics
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Control Module References Control Module References for body control module (BCM) or control solenoid valve assembly replacement, setup and programming
* Transmission Control Replacement Transmission Control Replacement