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P2780 OBD-II Trouble Code: Downshift Switch Circuit Low

Check Engine Light

P2780 code definition

This code is applied to all manufacturers, and it means that the downshift switch circuit is low. The upshift and downshift switch are found near the shifter in the passenger compartment. Most of the time these types of switches are used in vehicles that have manually shifting automatic transmissions.

What the P2780 code means

When this trouble code appears, it means that the PCM has found an issue with the downshift switch circuit’s electrical circuit. There are a number of different elements that are included within this circuit. These include the mode actuator, the wiring and connectors in the system, as well as the switch.

Whenever the powertrain control module detects the voltage in the downshift switch circuit that does not meet the specifications from the manufacturer, it will store the trouble code.

What causes the P2780 code?

The following are some of the most common causes of the P2780 code.

  • Corroded electrical wiring
  • Liquid spilled on the upshift/downshift switch
  • Shorted electrical wiring
  • Damaged or disconnected wiring

What are the symptoms of the P2780 code?

In most cases, there are not going to be very many symptoms that are noticeable when the P2780 code appears. The manual shifter function will be disabled, which is going to be the most noticeable problem. In some cases, the transmission will not shift properly. It will shift roughly. In addition, the code will be stored. In some cases, the Check Engine Light will illuminate as well, but this usually only happens after multiple failures. It is also possible the Service Engine Light will never illuminate due to this code, even though the code might be present.

How does a mechanic diagnose the P2780 code?

Mechanics will diagnose the P2780 code just as a will any other trouble code. They will make use of their scanner, which they attach to the onboard computer of the vehicle. They then test to see what trouble codes have been stored. Then, they will reset the trouble code and run the vehicle to see if the code returns. If it does return, it means that there is a problem with the downshift switch circuit. They will then have a better idea of what they need to do in order to repair the vehicle to fix the code.

Common mistakes when diagnosing the P2780 code

One of the most common misdiagnoses when it comes to the P2780 code is believing that the problem must be in the transmission wiring. While it is possible that the transmission wiring could be the problem, it is generally more likely that the issue resulted from liquid spilled onto the switches. Mechanics should always look at the simplest solution first.

How serious is the P2780 code?

If you plan to manually shift your automatic transmission vehicle, the problem with this code means you no longer have that option. Therefore, you’ll want to get it fixed as soon as possible. If you do not drive your vehicle in this manner, you might not think it is necessary to have the code fixed. However, that is not the case. You should still make sure to take the vehicle to a mechanic to have it diagnosed properly and repaired so you can make sure there are no other issues.

What repairs can fix the P2780 code?

The following are some of the repairs and fixes that mechanics may need to employ in order to fix the P2780 code:

Additional comments for consideration regarding the P2780 code

The vehicle will no longer be able to manually shift, and you will have to rely on the automatic shifting, which can be a huge problem for many drivers. If this or any other code appears, get it repaired as quickly as possible.

Need help with a P0469 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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