P2779 Fault Code

Downshift Switch Circuit Range/Performance

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

The P2779 fault code indicates a problem with the downshift switch circuit's range or performance. This code is associated with the transmission control system in vehicles, specifically relating to the functionality of the downshift switch. When the downshift switch fails to operate correctly, it can disrupt the shifting patterns of the transmission.

What are the symptoms of the P2779 code?

Common symptoms associated with the P2779 code can include:

• Harsh or erratic shifting while driving.
• Failure to downshift when needed, leading to poor vehicle performance.
• Transmission warning lights illuminated on the dashboard.
• Decreased fuel efficiency due to improper gear selection.

What causes the P2779 code?

Several factors can lead to the P2779 code, including:

• A faulty downshift switch that may be stuck or malfunctioning.
• Wiring issues such as shorts, open circuits, or corrosion that hinder electrical signals.
• A problem with the transmission control module (TCM) or engine control module (ECM) not processing inputs correctly.
• Mechanical issues within the transmission that prevent it from downshifting properly.

How to fix P2779?

To resolve the P2779 fault code, consider the following steps:

• Inspect and test the downshift switch to ensure it’s functioning correctly.
• Check the wiring and connectors for any signs of damage, corrosion, or loose connections.
• Test the Transmission Control Module (TCM) for faults and reprogram or replace it if necessary.
• If mechanical issues are suspected, a transmission inspection may be required to identify and fix the problem.