Technical Description of OBD-II Trouble Code
Malfunction in the Upshift Switch Circuit
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to various OBD-II vehicles (1996-newer). This includes vehicles from Ford, Acura, Vauxhall, Aston-Martin, Mercedes-Benz, Sprinter, and others. While it is a generic code, the specific repair steps may differ based on the year, make, model, and powertrain configuration.
If your vehicle has stored a code P0815, it means that the powertrain control module (PCM) has detected a malfunction in the upshift switch circuit. This code is typically found in vehicles equipped with paddle shifters.
The transmission control module (TCM) may be a separate module or part of the PCM. Upshift (paddle) shifter buttons are usually located on the steering wheel horn pad near the driver’s fingers. They are used as a type of sport shifter, commonly found in high-performance models. The PCM monitors the transmission gear selection in comparison to the upshift switch input signals to ensure continuity. Additionally, the PCM monitors the upshift switch circuit voltage to ensure it falls within the established parameters.
If the PCM detects that the transmission gear selection does not match the gear selection signal input from the upshift switch, or if the switch circuit voltage is outside the allowable parameters, a code P0815 may be stored and the malfunction indicator lamp (MIL) will illuminate. Multiple ignition cycles (with a failure) may be necessary for the MIL to illuminate.
What is the severity of this DTC?
A stored code P0815 indicates that either a serious electrical issue or some type of mechanical failure has occurred. In any case, it is important to rectify the conditions that led to the storage of this code as quickly as possible.
What are some of the symptoms of the code?
Symptoms of a P0815 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P0815 troubleshooting steps?
To diagnose a code P0815, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and access to vehicle-specific diagnostic information.
You can use your source of vehicle information to find a technical service bulletin (TSB) that matches the vehicle’s year, make, and model, as well as the engine size, stored code/s, and exhibited symptoms. If you find a relevant TSB, it may provide helpful diagnostic information.
Connect the scanner to the vehicle diagnostic connector to retrieve all stored codes and relevant freeze frame data. It is recommended to write down this information before clearing the codes, and then test-drive the vehicle until the PCM either enters readiness mode or the code is reset.
If the PCM enters readiness mode at this point, the code is intermittent and may be more challenging to diagnose. In such cases, the conditions that led to the storage of the code may need to worsen before an accurate diagnosis can be made.
If the code is immediately reset, the next step in your diagnosis will involve consulting your vehicle information source for diagnostic flowcharts, connector pin-out charts, connector face views, and component testing procedures/specifications.
Step 1
Use the DVOM to test the voltage, ground, and signal output at the appropriate upshift switch. Typical upshift switch circuits consist of either battery voltage (when activated) or ground (when deactivated).
Step 2
If the system circuits are functioning properly, use the DVOM to test the upshift switch circuits to the PCM or transmission. Disconnect all controllers before using the DVOM for testing.
Step 3
Use your source of vehicle diagnostic information and the DVOM to test the upshift switches as required. Replace switches that do not meet the system specifications.
