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P0815 OBD-II Trouble Code: Upshift Switch Circuit

check engine light

What the P0815 code means

Your vehicle’s powertrain control module (PCM) has recognized a problem in the electrical circuit of the upshift switch circuit. The upshift/downshift switch is located in the passenger compartment near your vehicle’s shifter. Please note that upshift/downshift switches are available only on vehicles with manual transmissions.

If your PCM recognizes a voltage or resistance signal in your vehicle’s upshift switch circuit that is not within the manufacturer’s specifications, a P0815 code will be stored and your Check Engine light may come on.

What causes the P0815 code?

Typically, a P0815 code appears because liquids have leaked onto your vehicle’s upshift/downshift switch. Other causes may include shorted or open wiring, or corroded, damaged or disconnected wiring or connectors.

What are the symptoms of the P0815 code?

One of the problems with a P0815 codes is that you may not notice any symptoms aside from a disabled manual shifter function. Your vehicle’s transmission may also slip into limp-in mode, which causes the transmission to shift harshly and your torque converter will no longer lock up as it should. Your Check Engine Light may come on after multiple failures.

How does a mechanic diagnose the P0815 code?

You will need a scanner and a digital volt/ohmmeter to diagnose this issue. As always, visually inspect all connectors and wiring, and keep an eye out for burned or shorted wiring. Replace or repair any wiring that appears to be corroded, damaged, or shorted. If the system wiring appears to be in bad shape, you may need to replace your full internal transmission harness. If your system wiring appears to be working well, then connect your scanner to the diagnostic connector and record all freeze frame data and trouble codes.

After you have cleared the codes, start your vehicle and check to see if the code reappears. If the code does not reappear immediately, your vehicle probably has an intermittent condition. However, if the code does immediately reappear, and the transmission seems to operate correctly, you should check for and ground signals and reference voltage at the actuator and upshift switch.

Be cautious when you are testing for continuity and resistance in wiring circuits, and make sure you disconnect all related controllers before performing any tests. Also, make sure that you consult your manufacturer’s wiring diagram for the upshift selector system, and that you test all related switches and circuits for continuity and resistance. Lastly, compare your results with your manufacturer’s specifications. If your upshift solenoid functions correctly and all circuits are aligned with manufacturer’s specifications, you may have a defective PCM.

Common mistakes when diagnosing the P0815 code

Many technicians overlook spilled liquids in the engine, and instead focus on wiring malfunctions in the transmission.

How serious is a P0815

Although a P0815 is not as serious as some other codes, you will still need to take your vehicle to a trained technician as soon as you see signs of a malfunction. If you decide to do the repairs yourself, please beware that there is a high danger of injury due to the number of wires you will be dealing with. Also, diagnosing a P0815, which can be especially difficult to detect, requires specialized and often expensive equipment. If you do not have this specialized equipment to diagnose the problem, your best bet is to consult a trained technician and have him or her solve the issue for you.

What repairs can fix the P0815 code?

This obviously depends on what issue your vehicle is having. You may have a PCM failure, which, although rare, requires replacement of your PCM and subsequent reprogramming. However, if your transmission mode selector fails, you will need to replace your normal/performance switch and then retest your vehicle’s transmission control system.

Additional comments for consideration regarding the P0815 code

In some cases, a P0815 will prevent your car from operating smoothly and shifting gears the way it was designed to do. Obviously this is something that you will want to fix right away. But please note that fixing this issue can become very difficult and that doing the repairs on your own may involve long periods of labor with costly diagnostic tools. Therefore, it is important to do the correct amount of research before you begin to work. Read as much as you can, and do not be afraid to consult a trained technician with any questions you may have.

Need help with a P0815 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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