P2778 Fault Code

Upshift Switch Circuit Intermittent/Erratic

• What does that mean?
• Symptoms
• Causes
• Solutions

The P2778 fault code indicates a problem with the upshift switch circuit in the vehicle's transmission system. This code suggests that there is an intermittent or erratic signal from the upshift switch, which is responsible for indicating when to shift gears up during operation. A faulty upshift switch can lead to improper gear changes, potentially affecting drivability.

What are the symptoms of the P2778 code?

Common symptoms associated with the P2778 fault code may include:

• Irregular shifting behavior, where the transmission may hesitate or shift at inappropriate times.
• Warning lights on the dashboard, such as the check engine light or transmission light.
• A noticeable decrease in fuel efficiency due to improper gear changes.
• Difficulty in accelerating or maintaining speed due to transmission confusion.

What causes the P2778 code?

Several factors can cause the P2778 fault code, including:

• A defective upshift switch that fails to send accurate signals.
• Damaged or corroded wiring and connectors within the upshift switch circuit.
• Software or calibration issues within the transmission control module (TCM) that may misinterpret the signals.
• Environmental factors, such as moisture or dirt entering the switch assembly, can cause erratic behavior.

How to fix P2778?

To resolve the P2778 fault code, consider the following steps:

• Inspect and test the upshift switch for proper functionality, and replace it if found defective.
• Check the wiring and connectors for any signs of damage or corrosion, repairing or replacing them as necessary.
• Ensure that the transmission control module (TCM) software is up-to-date and correctly calibrated.
• Conduct a thorough inspection for moisture or dirt in the switch area, cleaning as needed to restore proper function.