Modern automatic transmissions are anything but simple. The everlasting race for ultimate efficiency has forced car manufacturers to pack transmission systems full of all kinds of sensors and electronics. 

As a result, modern automatic transmissions can experience a whole range of issues, each of them with its own corresponding check engine light code. In this particular instance, we’ll be looking at the P0780 error code which stands for “shift malfunction”. We’ll discuss what this code actually means, what causes it, the most common symptoms and how to get it fixed. 

What Does P0780 Code Mean? 

Unlike other diagnostic trouble codes (DTC) that have a very obvious and specific cause, the P0780 is more indicative of a general issue with the transmission. It means that your transmission control module, a small computer that governs your transmission, has logged an abnormal gear shift. What has caused the abnormal shift or why it happens is not something this error code will point out on its own. 

And that’s okay because this particular error is usually followed by one or more additional transmission-related errors such as P0781 to P0784. These four codes each point to a different gear shift sequence. For instance, P0781 is triggered when there’s an abnormal shift between the 1st and 2nd gear, while P0782 is triggered when an abnormal 2nd to 3rd gear shift is logged by the TCM. 

The presence of additional codes will often give you a much better idea of where to start looking. If there are no other codes stored in the ECU when you do a full scan, you’ll most likely have to test the whole system to find what’s causing the issue. Speaking of which… 

What Causes the P0780 Error? 

There is a wide range of issues that can trigger the P0780 code. These range from something as simple as low transmission fluid levels, to something as severe as a faulty TCM. However, the more severe cases are often the most uncommon. The common causes can be separated into two categories – mechanical and electrical. 

Mechanical causes of the P0780 include the following 

• Low transmission fluid
• Old or contaminated transmission fluid
• Blockage in the transmission system that prevents circulation of fluid
• Transmission fluid pump issues
• Internal transmission component failure 

Electrical causes include: 

• Failed shift solenoids 
• Electrical harness issues
• Electrical connector failure 
• ECU or TCM failure 

Figuring out which type of issue is causing the shift malfunction will mainly come down to the symptoms you’re experiencing. 

Common Symptoms 

There are many symptoms related to this particular diagnostic trouble code and almost all of them will affect your driving experience to some extent. Here are the most common issues you’ll likely experience when dealing with the P0780 DTC. 

• Check engine light
• Harsh shifting between some, or all gears
• Unpredictable shifting patterns 
• Slipping transmission 
• Whining noise coming from the transmission 

As it just so happens, most of these symptoms are caused by improper transmission maintenance, which implies old fluid, clogged filters, and generally poor condition of the transmission. 

That being said, let’s see how you can diagnose exactly what’s causing you all this trouble. 

How to Troubleshoot the P0780 Code 

Diagnosing shift malfunction codes comes down to doing a full scan and assessing the situation from there. Then, you have the decision to either start by troubleshooting the mechanical or electrical systems first. Here’s the troubleshooting order we recommend. 

Run a Full OBD II Scan 

First thing first, get your OBD II scanner and run a complete scan. Most modern scanners, even the cheap ones, will be able to pick up a wide range of transmission codes. That being said, the better the scanner you have, the more info you’ll be able to read from your car. Anyway, run a full scan and see what comes back. 

If you’re only getting the P0780 code and nothing else, you’ll need to run through the entire troubleshooting process. If you’re getting this code followed by another code such as the P0781 or similar, you can narrow down the issue to a few specific components. 

Check the Fluid 

Next, you’ll want to check your transmission fluid. Your fluid needs to be present in an adequate amount and be in good condition. If you pull out the dipstick and find no fluid on the stick, chances are you’ve found what’s causing your problem. Similarly, if the fluid is present on the dipstick, but is dark in color and smells like it’s burnt, that’s also not good. 

Most mechanics will tell you that if your vehicle has been properly maintained, you shouldn’t run into these issues. That being said, there are instances where car manufacturers’ transmission service cycles were overly optimistic, to put it lightly, causing owners to run their transmissions into the ground. That’s why it’s always a good idea to stay on top of the latest service recommendations for your specific vehicle. 

In case you’ve found any issues with the transmission fluid, do a complete service and change the fluid/filter. If that doesn’t fix your problem, move on to the next part of this guide. 

Check the Electronics 

Checking the electronics is often much easier than checking the mechanical components of the transmission. Start by inspecting the wiring harnesses that run to and from the transmission. Make sure to pay close attention to any wiring that is close to the exhaust manifold as these segments of the wiring harness usually suffer severe heat exposure. 

Next, check the connectors. Visually inspect each one for damage. If you suspect that any of the connectors are going bad, it could be a good idea to test them using a multimeter. The process requires a basic understanding of automotive electronics and the use of a said multimeter. If you’re not comfortable doing this, it’s best you leave it to someone who has experience in these matters. 

If the wiring and connectors look good, it’s time to turn to your shift solenoids. 

Shift Solenoids 

A shift solenoid is an electromechanical component whose main job is to allow or disallow the passage of transmission fluid as dictated by the TCM. When the shift solenoid opens up, the transmission will shift the corresponding gears. Modern transmissions feature two or more shift solenoids, depending on the make and model of your vehicle. 

Testing shift solenoids usually means dismounting them from the car. Many vehicles use externally mounted shift solenoids, but some have these solenoids mounted on the inside of the transmission. Inspect the solenoid O-rings for wear and make sure that the electrical part of the assembly is activating. 

Shift solenoid failure is usually accompanied by P0750-P0774 errors, all of which are related to this component. 

Checking for Mechanical Issues 

Checking for mechanical causes such as a bad ATF pump can be tricky. Doing almost anything of this nature will require you to tear down the transmission. If the transmission fluid test shows that there are issues and your electrical components appear to be good, you should probably make an appointment with a transmission specialist near you. 

Service Your Transmission Using Quality Parts! 

Dealing with transmission-related codes such as the P0780 is never fun. However, most issues that trigger this particular DTC can be prevented by following the proper transmission service intervals and using quality parts. 

Here at eEuroparts.com, we offer a wide range of top-tier transmission fluids, filters, transmission pan gaskets, and everything else you could need to service or repair your transmission. Head over to our store, select your vehicle, and navigate your way to the transmission section. You’ll find everything you need there, and then some!