P2779 OBD-II Trouble Code: Downshift Switch Circuit Range/Performance

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Cost of diagnosing the P2779 code

P2779 is a diagnostic trouble code (DTC) for "Downshift Switch Circuit Range/Performance". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light is on diagnostic inspection. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

P2779 code definition

P2779 Trouble Code is for the downshift switch circuit range and performance, and it sets when the voltage or resistance signal is not within the specified range provided by the manufacturer.

What the P2779 code means

The code means there is an issue with the downshift switch. Only vehicles that have manually shifting automatic transmissions will have this code appear. In some instances, it will take multiple failure cycles before this code causes the malfunction light to come on in the vehicle.

What causes the P2779 code?

The following are some of the most common causes of the P2779 code:

  • Liquids being spilled on the upshift/downshift switch

  • Wiring and connector issues – damaged, corroded, shorted, or disconnected connectors or wiring

What are the symptoms of the P2779 code?

In many cases, the symptoms will be very limited, and many drivers may not notice any issues with their vehicles. They will find that the manual shifter function of the vehicle is not working, or that it places the transmission in limp-home mode. If this happens, it will be much easier to realize something is wrong with the vehicle. The vehicle will have a hard time shifting, for example.

How does a mechanic diagnose the P2779 code?

To diagnose the P2779 code, the mechanic will want to connect their OBD-II scanner to the vehicle’s onboard computer. This computer gathers data about the car, and it makes it possible to share that data with the scanner. Naturally, this will make diagnosing the problem with the vehicle much easier. The mechanic will also reset the vehicle and drive it. They do this to see whether the code returns or not. When the code returns, they know that it is something that is actually wrong with the vehicle and it was not triggered by mistake. They can then start their diagnosis on that particular issue.

Common mistakes when diagnosing the P2779 code

One of the biggest mistakes when diagnosing the P2779 code is forgetting that the most common reason for the problem is spilling liquid onto the upshift/downshift switch. Instead of addressing this issue, they believe that the transmission wiring has malfunctioned instead. It is important to look at the most likely cause when diagnosing and repairing vehicles.

How serious is the P2779 code?

It is always important to take your vehicle to a mechanic for regular tune-ups as well as when there is an issue with your vehicle. This is true even if your vehicle still seems to be running well. If you find that there are codes stored in the vehicle, you want to get them diagnosed and taken care of right away. While the P2779 code might not seem too serious, it has the potential to cause some issues with your ability to shift properly. That’s not something you want to deal with.

What repairs can fix the P2779 code?

The following are some of the repairs that mechanics might use when they repair the P2779 code:

  • Check the upshift/downshift switch for damage caused by liquids and repair or replace it.

  • Check the wiring for corrosion, shorts, and bad connections and repair as needed.

  • Replace the powertrain control module

Additional comments for consideration regarding the P2779 code

Keep in mind that it is very rare for the powertrain control module to be at fault in these cases. It is usually the result of spilling liquid on the upshift/downshift switch. If you have noticed any issues with your vehicle, or if you know that you have the code stored in your vehicle, don’t wait on getting it repaired. Even though it might not be causing you any issues when you are driving now, you don’t want to have the problem get worse. Take your vehicle to a mechanic as quickly as possible to get the repairs the vehicle needs.

Need help with a P2779 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.

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P2779
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Nazareth

26 years of experience
168 reviews
Nazareth
26 years of experience
Mercedes-Benz CLA250 - Check Engine Light is on - Los Angeles, California
Polite and very professional! Nazareth quickly identified my car was suffering from low voltage issues and the battery was the problem. The reader was showing 8 volts hence why my car didn’t receive enough power to start, it needed 12v. My battery was 4 years old and never been changed. Thank you Nazareth!

Cornelius

17 years of experience
78 reviews
Cornelius
17 years of experience
Chevrolet Cobalt - Check Engine Light is on - Peachtree City, Georgia
He was very helpful with explaining what could lead to my check engine light being on. And helping clear my engine light.

Marco

28 years of experience
78 reviews
Marco
28 years of experience
Nissan Maxima - Check Engine Light is on - Highland, California
Marco did a great job of finding the source of the problem and his recommendations were greatly appreciated.

Juan

8 years of experience
128 reviews
Juan
8 years of experience
Chevrolet Tahoe - Check Engine Light is on - Altamonte Springs, Florida
Juan was on time for both appointments. He was knowledgeable and polite and I will most definitely be requesting him for my next steps based on the quote he provided me for other issues I need to address. Excellent customer service and top notch repair work!


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