6L45/6L50/6L80/6L90 - Automatic Transmission
DTC P0815, P0816, P0826, or P1876
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
DTC P1876
- Up and Down Shift Enable Switch Circuit Low Voltage
Diagnostic Fault Information
Circuit/System Description
The driver shift request (DSR), also known as the TAP Up/Downshift manual shift function, allows the driver to select the desired range of gears for current driving conditions. The DSR shift system is activated when the gear selector is in the manual position. The DSR system is deactivated in all other range positions. Pressing the plus (+) switch once will command the body control module (BCM) to signal the transmission control module (TCM) to upshift to the next high gear. Pressing the minus (-) switch once will command the BCM to signal the TCM to downshift to the next lowest or previous gear. The TCM will not allow a downshift if the transmission is compromised by over-speeding. The automatic transmission manual shift switch is comprised of three different resistors values in series and two switches. The BCM supplies a 12 volt circuit to the automatic transmission manual shift switch. The signal circuit varies the voltage back to the body control module depending on which switch is depressed.
Conditions for Running the DTC
P0815, P0816 or P0826
* DTC P0815, P0816, P0826, P182E, P1876, P1877, P1915 or P1761 is not set.
* The ignition voltage is 8.6 volts or greater.
* The engine speed is 400 RPM or greater for 5 seconds.
P1876
* DTC U0100, P0815, P0816, P0826, P1825, P1876 or P1915 is not set.
* The ignition voltage is 8.6 volts or greater.
* The engine speed is 400 RPM or greater for 5 seconds.
Conditions for Setting the DTC
P0815 - Condition 1
The BCM detects a stuck ON Tap Up switch for 1 second in Park or Neutral.
P0815 - Condition 2
The BCM detects a stuck ON Tap Up switch for 10 minutes in any forward gear.
P0816 - Condition 1
The BCM detects a stuck ON Tap Down switch for 1 second in Park or Neutral.
P0816 - Condition 2
The BCM detects a stuck ON Tap Down switch for 10 minutes in any forward gear.
P0826
The BCM detects an invalid voltage on the TAP up/down signal circuit for 1 minute.
P1876
The BCM detects a TAP Enable Switch request 3 times when not in M (D6) range for 2 seconds.
Action Taken When the DTC Sets
* DTCs P0815, P0816, P0826, and P1876 are Type C DTCs.
* The BCM disables TAP shift operation.
Conditions for Clearing the DTC
DTCs P0815, P0816, P0826, and P1876 are Type C DTCs.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (6L45/6L50/6L80/6L90 - Automatic Transmission)
Connector End View Reference
* Component Connector End Views (Connector End Views By Name)
* Inline Harness Connector End Views (Connector End Views By Number)
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)
Scan Tool Reference
Control Module References (Control Module References) for scan tool information
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Circuit/System Verification
1. Ignition ON, verify with a scan tool the Tap Up/Down Switch parameter displays ON in the Chassis Data list under BCM.
2. Ignition ON, verify with a scan tool the Tap Up/Down parameter displays UP when pressing the plus (+) switch and Down when pressing the minus (-) switch.
3. Ignition ON, verify with a scan tool the Driver Shift Control parameter in the Transmission Data list changes from, Inactive to Active when placing the automatic transmission shift lever in manual mode position.
4. Ignition ON, verify with a scan tool the Driver Shift Request Switch 1 displays NONE in the transmission data list.
5. Ignition ON, verify with a scan tool the Driver Shift Request Switch 1 displays Upshift when pressing the plus (+) switch and Downshift when pressing the minus (-) switch.
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, disconnect the automatic transmission shift lever harness connector.
2. Ignition ON, verify with a scan tool the Tap Up/Down Switch parameter displays OFF in the Chassis Data list under BCM.
3. Ignition ON, test for greater than 11 volts between the ignition voltage circuit terminal 4 and ground at the battery negative post.
• If less than the specified value, test the ignition voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
4. Ignition OFF, test for 6.6-7.0 K ohms between terminal 3 and terminal 4 on the automatic transmission shift lever harness connector. Also, test for 3.7-4.2 K ohms when pressing the minus (-) switch and 1.7-2.0 K ohms when selecting the plus (+) switch.
• If not within the specified values, replace the automatic transmission shift lever.
5. Test the signal circuit between the BCM and the automatic transmission manual shift switch for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Replace the RSM shift switch. Refer to Shift Lever Replacement (Shift Lever Replacement).
* Replace the BCM. Refer to Control Module References (Control Module References) for replacement, setup, and programming