P0815
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 pushing the shift lever forward for an upshift or pulling the shift lever rearward for a downshift. The body control module (BCM) supplies battery voltage, ground, and a signal circuit to the shift controller. The shift controller has Hall-effect switches connected to a resistor array. When the lever is in the M position, then pushed forward for an upshift, or pulled rearward for a downshift, a corresponding voltage drop occurs across the resistor network. This voltage drop is monitored by the BCM. The BCM will send the request to the transmission control module to perform the upshift or downshift.
Conditions for Running the DTC
P0815
* The engine speed is greater than 500 RPM for at least 5 seconds.
* The ignition voltage is greater than 9.0 volts.
* No DTCs P0815, P0826, P1761, P182E, P1876, P1877, or P1915.
* The time since the last range change is greater than 1 second.
P0816
* The engine speed is greater than 500 RPM for at least 5 seconds.
* The ignition voltage is greater than 9.0 volts.
* No DTCs P0816, P0826, P1761, P182E, P1876, P1877, or P1915.
* The time since the last range change is greater than 1 second.
P0826
* The engine speed is greater than 500 RPM for at least 5 seconds.
* The ignition voltage is greater than 9.0 volts.
Conditions for Setting the DTC
P0815 - Condition 1
The transmission control module (TCM) detects an upshift request for 1 second or greater in PARK, REVERSE, or NEUTRAL.
P0815 - Condition 2
The TCM detects an upshift request for 10 minutes.
P0816 - Condition 1
The TCM detects a downshift request for 1 second in PARK, REVERSE, or NEUTRAL.
P0816 - Condition 2
The TCM detects a downshift request for 10 minutes.
P0826
The TCM detects an invalid voltage on the TAP up/down signal circuit for 1 minute.
Action Taken When the DTC Sets
P0815, P0816, P0826
* DTCs P0815, P0816, and P0826 are Type C DTCs.
* The TCM inhibits Tap Up/Down function.
Conditions for Clearing the DTC
P0815, P0816, P0826
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)
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. Ignition ON, observe the scan tool Driver Shift Control parameter, while moving the transmission shift through the park, reverse, neutral and drive positions. The reading should display Inactive.
2. Shift lever in the M position, observe the scan tool Driver Shift Request parameter while pushing the shift lever forward and pulling the shift lever rearward. The parameter should change from None to Upshift or 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 shift lever assembly electrical connector from the shift lever assembly.
2. Test for less than 10 ohms between the shift lever harness connector terminal 2 and ground.
• If greater than the specified range, repair the ground circuit.
3. Ignition ON, verify the scan tool Driver Shift Control parameter displays inactive.
• If not the expected results, test the signal circuit between shift lever assembly connector terminal 3 and the BCM for a short to voltage or ground. If the circuit tests normal, replace the BCM.
4. Ignition OFF, connect a test lamp between shift lever harness connector B+ terminal 1 and ground circuit terminal 2.
5. Ignition ON, verify the test lamp is illuminated.
• If the light stays off, test the B+ circuit for an open/high resistance. If the circuit tests normal, replace the BCM.
6. Test for 11-13 volts at the shift lever assembly harness connector between signal circuit terminal 3 and ground.
• If not within the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
7. Ignition OFF, connect the shift lever harness connector.
8. Ignition ON, back probe the shift lever assembly connector and test for 11-13 volts between terminal 3 and ground with the shift lever in park, reverse, neutral, and drive.
• If not within the specified range, replace the shift lever assembly.
9. Use a DMM to monitor the voltage between shift lever assembly connector terminal 3 and ground, with the shift selector in the M, tap up, and tap down position. Compare the readings and verify the voltages are correct for each position as follows:
* Manual: 8.0-10.6 volts
* Tap down: 5.1-7.3 volts
* Tap up: 2.0-4.6 volts
• If not within the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the shift lever assembly.
10. If all circuits test normal, replace the BCM.
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.
* Refer to Transmission Control Replacement (Transmission Control Replacement) for AT TAP shift switch replacement.