OBD-II code · Powertrain (generic, extended)
P2779 Downshift Switch Circuit Range/Performance
The downshift switch signal is implausible. Stuck or noisy contacts. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
Is it safe to drive with P2779?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- PossibleContamination on switch contacts
- PossibleWorn switch contacts
- Less likelySensor element aged beyond calibration window
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.5–2.5 h
- Emissions test
- Usually unaffected
- Parts involved
- Downshift Switch, Steering Wheel Controls
Related codes
- P2776Upshift Switch Circuit Low
- P2777Upshift Switch Circuit High
- P2778Upshift Switch Circuit Intermittent/Erratic
- P277AElectric/Auxiliary Transmission Fluid Pump B Hydraulic Leakage
- P277BElectric/Auxiliary Transmission Fluid Pump B Driver Circuit Performance
- P277CElectric/Auxiliary Transmission Fluid Pump B Motor Stalled
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.