P0780 Code: Shift Malfunction

There are several diagnostic trouble codes related to the transmission. One of them is code P0780.

What Does the P0780 Code Mean?

P0780 stands for “Shift Malfunction.” It’s a generic diagnostic trouble code that usually applies to OBD-II-equipped vehicles from Ford, Honda, Mazda, Volkswagen, and other manufacturers.

Code P0780 is only applicable for vehicles with automatic transmissions. The code may register on your scan tool if your powertrain control module (PCM) detects a problem with your automatic transmission system.

The transmission controller uses input and output speed sensors to determine if the hydraulic pressure in the transmission matches the appropriate RPM and engine load. Any mechanical or electronic malfunction during this process may trigger a P0780 code.

P0780 on Some Mazda Vehicles

Mazda describes the P0780 detection strategy as follows:

1. If gear ratio malfunction or clutch-slip occurs while in any forward gear and vehicle is driven while gear ratio fail-safe is engaged or there is forced use of gear speeds in which clutch slip occurs is restricted.
2. If the TCM has determined that the vehicle may have a damaged clutch due to the clutch not engaging when the TCM directs engagement according to oil pressure switch input.

Hydraulic Pressure in the Transmission

Automatic transmissions apply their clutch pack assemblies using hydraulic pressure controlled within the transmission. The heart of this kind of automatic transmission are planetary gear sets, each of which consists of a sun gear, planet gears, and a ring gear. Older transmissions had only one planetary gearset while newer transmissions have more than one.

Holding and driving different parts of these gear sets provides all gear ranges, including reverse. If, for some reason, a holding or driving clutch is not fully applied and begins to slip, the PCM instantly detects the slippage.

There isn’t much lining on those clutches, and it’s very easy to burn them out. That’s why the default is to “max out” the line pressure used to apply the clutches, which typically causes harsh shift engagements, but the higher pressure during clutch application will also protect the clutches from slipping unless they’ve already lost their lining. So, this is for the elimination (if possible) of slipping.

Note:  The definition of P0780: Shift Malfunction may vary depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact definition.

What are the Possible Causes of P0780?

A P0780 code may be triggered due to the following causes:

• Low transmission fluid
• Old or burnt transmission fluid
• Faulty shift solenoid/s
• Malfunctioning input or output speed sensors
• Transmission control harnesses have shorted or open circuits
• Defective electronic pressure regulator
• Bad transmission pump
• Mechanical failure
• Defective PCM

What are the Common Symptoms of the P0780 Code?

A malfunctioning transmission shift may exhibit the following symptoms:

• Illuminated check engine light
• Erratic shifting
• Delayed shifting
• Rough shifting
• Slipping
• Whining noise from transmission

How to Diagnose the P0780 Code

A P0780 code can be difficult to diagnose because some of its causes and symptoms may overlap with other diagnostic trouble codes.

How to Fix the P0780 Code

Not all vehicles are the same. Some makes and models have specific instructions for fixing the problems that trigger a  P0780. If you don’t follow the procedures in your vehicle’s repair manual, you can end up damaging your ride’s internal components. Before attempting any repairs, you first need to identify the underlying causes that have triggered the P0780 code.

If you decide to fix the code yourself, you’ll need to conduct an accurate diagnosis of your vehicle to figure out what repairs are needed. We highly recommend using online auto repair resources to educate yourself on specific OBD-II codes. ALLDATA has single-vehicle subscriptions that include detailed factory repair information.

You can also bring your vehicle to the nearest repair shop and have it checked by a trained professional. They can give you a complete breakdown of your vehicle’s issues and perform the necessary repairs, so that you don’t have to do it yourself. This is an excellent option if you don’t mind paying for labor.