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
Typical Scan Tool Data
Circuit/System Description
When the shift lever is placed in manual mode (M) this activates the driver shift request (DSR), also known as the tap shift function. The DSR allows the vehicle operator to shift gears by pressing the plus (+) button for an upshift or the minus (-) button for a downshift. A 12 volt signal circuit is provided by the body control module (BCM) to the plus or minus buttons. When a plus or minus button is pressed, a corresponding voltage drop occurs across the resistor network embedded in the switches. This voltage drop is monitored by the BCM. The BCM will send the request to the transmission control module (TCM) to perform the upshift or downshift.
Conditions for Running the DTC
P0815 or P0816
* DTC P0815, P0816, P0826, P1761, P182E, P1876, P1877, or P1915 is not set.
* The time since the range change is 1 second or greater.
* 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 400 RPM or greater for 5 seconds.
* The ignition voltage is 8.6 volts or greater.
* DTC P0826 or P1761 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/Tap down signal circuit for 1 minute.
Action Taken When the DTC Sets
* DTCs P0815, P0816, and P0826 are Type C DTCs.
* The TCM inhibits Tap Up/Down function.
* The TCM inhibits manual shifting of forward gears.
Conditions for Clearing the DTC
DTCs P0815, P0816, and P0826 are Type C DTCs.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (Diagrams)
Connector End View Reference
* Component Connector End Views (Connector Views)
* 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 (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Driver Shift Control Mode parameter while moving the transmission shift lever through all the positions. The parameter should display Inactive in the park, reverse, neutral, and drive positions, and Active in the M position.
2. Shift lever in the M position, verify the scan tool Driver Shift Request parameter changes from None to Upshift when the plus button is pressed, and from none to Downshift when the minus button is pressed.
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 Mode 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 lever in the M position, with the tap up plus button depressed, and the M position with the tap down minus button depressed. 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
Note:
* Perform the Transmission Adaptive Values Learn (Transmission Adaptive Values Learn) 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)