P2780
Downshift Switch Circuit Low
Transmission controls
Generic OBD-II
Low
What it means
P2780 means the transmission controller sees an abnormally low (shorted-low) voltage on the driver's downshift switch circuit — the button or paddle used to command a manual downshift. The automatic still shifts on its own, so this is usually a minor, feature-loss fault caused by a bad switch, a short in the wiring, or moisture in the connector.
Low
Can I keep driving? Usually yes — the automatic still shifts on its own; you mainly lose manual/tap downshift control until it's fixed.
Common symptoms
What you'll notice
- Check-engine light on
- Manual/tap-shift downshift button or paddle does nothing
- Transmission may not respond to a requested manual downshift
- Gear-selector or shift indicator may behave oddly in manual mode
Common causes
Most likely first
- Downshift switch shorted to ground or internally failedLikely
- Chafed or pinched wiring shorting the signal wire lowCommon
- Corroded or wet connector at the shift switch (spilled liquid on console)Common
- Faulty TCM/PCM input circuit (least likely)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame and confirm the code is current, not a one-time glitch.
- Inspect the downshift switch and its connector for moisture, corrosion, or damage.
- Check the switch signal wire for a short to ground and repair any chafed or pinched harness.
- Test the switch operation with a meter against the service value; replace the switch if out of spec.
- Clear the code and re-test the manual downshift function.
FAQ
Quick answers
Is it safe to drive with P2780?+
Generally yes. The transmission still shifts automatically; you're mainly losing the manual downshift request until the switch or wiring is repaired.
Can I just clear P2780?+
You can, but if the switch or its wiring is shorted the code returns. Fix the circuit so manual downshift works again.
Related codes
Often seen with P2780
Read & clear P2780 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX