P0815 Upshift Switch Circuit
OBD-II Trouble Code Technical Description
ASE Certified Technician
Upshift Switch Circuit
What does that mean?
总裁俱乐部appThis diagnostic trouble code (DTC) is a generic powertrain code and applies to many OBD-II vehicles (1996-newer). That may include but is not limited to vehicles from Ford, Acura, Vauxhall, Aston-Martin, Mercedes-Benz, Sprinter, etc. Although generic, the exact repair steps may vary depending on 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 type of code is usually limited to vehicles with paddle shifters.
The transmission control module (TCM) may be a stand alone module or part of the PCM. Upshift (paddle) shifter buttons are typically located on the steering wheel horn pad in close proximity to the driver’s finger position. They are used as a type of sport shifter, usually in high-performance models. The PCM monitors transmission gear selection in comparison to upshift switch input signals to ensure continuity. Additionally, the PCM monitors upshift switch circuit voltage to ensure that is within established parameters.
If the PCM detects that the transmission gear selection is not conducive to the gear selection signal input by the upshift switch or if switch circuit voltage is not within allowable parameters, a code P0815 may be stored and a malfunction indicator lamp (MIL) illuminated. Multiple ignition cycles (with a failure) may be required for MIL illumination.
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. At any rate, conditions which contributed to a code of this nature being stored should be rectified as quickly as possible.
What are some of the symptoms of the code?
总裁俱乐部appSymptoms of a P0815 trouble code may include:
- Manual (paddle) upshift function disabled
- Shift indicator reflects incorrect gear
- No symptoms may be exhibited
What are some of the common causes of the code?
总裁俱乐部appCauses for this code may include:
- Defective upshift switch
- Shorted or open circuits in upshift switch circuit
- Faulty PCM or a programming error
What are some P0815 troubleshooting steps?
A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle specific diagnostic information will be required to diagnose a code P0815.
You may use your source of vehicle information to locate a technical service bulletin (TSB) that matches the vehicle year, make, and model; as well as the engine size, code/s stored, and symptoms exhibited. If you find one, it could yield helpful diagnostic information.
Use the scanner (connected to the vehicle diagnostic connector) to retrieve all stored codes and pertinent freeze frame data. It is a good idea to write this information down before clearing the codes then test-drive the vehicle until the PCM either enters readiness mode or the code is reset.
总裁俱乐部appIf the PCM enters readiness mode at this time, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions which contributed to the code being stored may need to worsen before an accurate diagnosis can be made.
If the code is immediately reset, the next step of your diagnosis will require that you search your vehicle information source for diagnostic flow-charts, connector pin-out charts, connector face views, and component testing procedures/specifications.
Use the DVOM to test 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).
If system circuits are functional, use the DVOM to test upshift switch circuits to the PCM or transmission. Disconnect all controllers prior to using the DVOM for testing.
总裁俱乐部appUse your source of vehicle diagnostic information and the DVOM to test upshift switches as required. Replace switches that do not test within system specifications.
- Upshift switch codes are most often attributed to switch failure
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