P0826
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 Tap Up plus (+) button for an upshift or the Tap Down minus (-) button for a downshift. The body control module (BCM) provides ignition voltage and a signal circuit to the resistor network embedded in the shift lever assembly. When a plus or minus button is pressed, a corresponding voltage drop occurs across the resistor network. This voltage drop is monitored by the BCM. The BCM sends the shift request to the transmission control module (TCM). The TCM will command the upshift or downshift providing the operating conditions are correct.
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.
* DTC P0826 or 1761 is not set.
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.
P0816 - Condition 2
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 End Views By Number)
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 (Programming and Relearning)for scan tool information
Circuit/System Verification
1. If other DTCs are set, diagnose them first.
2. Ignition ON, engine OFF, transmission shift lever in Park, parking brake ON, 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. Observe the scan tool Driver Shift Request parameter. The reading should display None.
5. Press and release the Tap Up (+) switch, and the Tap Down (-) switch, while observing the scan tool Driver Shift Request 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.
6. 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, parking brake ON, disconnect the automatic transmission manual shift connector.
2. Ignition ON, engine OFF, verify that a test lamp illuminates between the ignition circuit automatic transmission manual shift harness connector terminal A 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. Ignition OFF, shift lever in park, test for an open circuit between the automatic transmission manual shift switch connector terminals A and B.
• If other than the specified value, replace the automatic transmission manual shift switch and lever assembly.
4. Shift lever in M, test for 6.5-7.1 k ohms between the automatic transmission manual shift switch connector terminals A and B. Verify the resistance changes to 1.7-2.1 k ohms when the Tap Up switch is pressed and 3.8-4.2 k ohms when the Tap Down switch is pressed.
• If not the specified value, replace the automatic transmission manual shift switch and lever assembly.
5. Test the signal circuit for open/high resistance or a short to voltage or ground.
• If circuit tests normal, replace the BCM.
Repair Instructions
Note:
* Perform the Service Fast Learn Adapts (Programming and Relearning) following all transmission related repairs.
* Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection).
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Control Module References (Programming and Relearning)for BCM or control solenoid valve assembly replacement, setup and programming
* Transmission Control Replacement Transmission Control Replacement