6T70 (M7W) - 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 the M position, electronic range select or manual mode, which allows for the selection of the range of gears available, is activated. This is also known as the tap shift function. Manual mode allows the vehicle operator to increase the highest transmission gear available by pressing the plus (+) button or decrease the highest gear available by pressing the minus (-) button. The body control module (BCM) supplies a signal circuit to the shift controller. The shift controller has switches connected to a resistor array. A voltage drop occurs across the resistor network. When the plus or minus button is pushed, 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 (TCM) to increase or decrease the available gear ranges. The TCM will not allow a downshift if the engine would be compromised by overspeeding.
Conditions for Running the DTC
P0815 or P0816
* DTC P0826, P1761, P182E, P1876, P1877, or P1915 is not set.
* Time since the range change is 1 s or greater.
* Engine speed is 400-7,500 RPM for 5 s.
* Ignition voltage is 8.6-32 V.
P0826
* DTC P1761 is not set.
* Engine speed is 400-7,500 RPM for 5 s.
* Ignition voltage is 8.6-32 V.
Conditions for Setting the DTC
P0815 - Condition 1
TCM detects an upshift request for 1 s in Park or Neutral.
P0815 - Condition 2
TCM detects an upshift request for 10 min in any forward range.
P0816 - Condition 1
TCM detects a downshift request for 1 s in Park or Neutral.
P0816 - Condition 2
TCM detects a downshift request for 10 min in any forward range.
P0826
TCM detects an invalid voltage on the Tap up/Tap down signal circuit for 1 min.
Action Taken When the DTC Sets
* DTCs P0815, P0816, and P0826 are Type C DTCs.
* TCM inhibits Tap Up/Down function.
* TCM inhibits manual shifting of forward gears.
Conditions for Clearing the DTC
DTCs P0815, P0816, and P0826 are Type C DTCs.
Diagnostic Aids
A high resistance in the signal circuit may not set a DTC. Symptoms could include an inoperative manual mode Tap Up/Down, or a Tap Down shift when the Tap/Up button is pressed.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics 6T70 (M7W) - Automatic Transmission
Connector End View Reference
* Component Connector End Views Sunshade - Left
* Inline Harness Connector End Views X110
Description and Operation
* Transmission General Description Transmission General Description
* Transmission Component and System Description Transmission Component and System Description
* Electronic Component Description Electronic Component 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
Warning: Refer to Parking Brake and Drive Wheels Warning Parking Brake and Drive Wheels Warning.
1. Ignition ON, engine OFF, Transmission Shift Lever in the M or manual mode position.
2. Verify the scan tool Up and Down Shift Switch or Driver Shift Request parameter displays Upshift when pressing the plus (+) switch, Downshift when pressing the minus (-) switch, and Inactive when neither switch is pressed.
• If the parameter does not display the correct value
Refer to Circuit/System Testing
• If the parameter displays the correct value
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
4. Verify the DTC does not set.
• If the DTC sets
Refer to Circuit/System Testing.
• If the DTC does not set.
5. All OK.
Circuit/System Testing
Note: You must perform the Circuit/System Verification first.
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the S3 Transmission Shift Lever. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 2 and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If greater than 2 ohms, repair the Open/High resistance in the circuit
• If less than 2 ohms, repair the ground connection
• If less than 10 ohms
3. Ignition ON.
4. Test for 11-13 V between the signal circuit terminal 3 and ground.
• If not between 11-13 V
1. Ignition OFF, disconnect the connector at the BCM.
2. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground in the circuit
• If infinite resistance
1. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the BCM.
• If between 11-13 V
5. Ignition OFF, connect the harness connector at the S3 Transmission Shift Lever, Ignition ON, transmission shift lever in the M or manual mode position.
6. Test for voltage between the S3 Transmission Shift Lever connector signal circuit terminal 3 and ground, by back probing the connector, for the conditions listed below:
* 2.0-4.6 V - Plus button pressed
* 5.1-7.3 V - Minus button pressed
* 8.0-10.6 V - Neither button pressed
• If voltage values are not correct
Replace the S3 Transmission Shift Lever
• If voltage valued are correct
7. Replace the K9 Body Control Module.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repairs.
* Perform the Reset Transmission Adapts Reset Transmission Adapts following all transmission repairs.
* Transmission Control Replacement Transmission Control Replacement
* Control Module References Control Module References for BCM or control solenoid valve assembly replacement, programming, and setup.