P0816
Downshift Switch Circuit
Transmission
Generic OBD-II
Low
What it means
P0816 means the transmission control module detected a fault in the downshift switch circuit — the driver input (paddle or shifter switch) used to request a manual downshift. The engine and normal automatic shifting are unaffected; usually only the manual downshift function may stop responding. The cause is typically a bad switch, wiring, or connector.
Low
Can I keep driving? The car drives normally — this is a driver-input switch, so at most the manual downshift function may not respond; get it looked at at your convenience.
Common symptoms
What you'll notice
- Check-engine light on
- Manual downshift (paddle or shifter) doesn't respond
- Manual/sport shift mode not working as expected
- No noticeable change to normal automatic shifting
Common causes
Most likely first
- Faulty downshift switchLikely
- Open, shorted, or chafed wiring in the switch circuitCommon
- Loose or corroded connector at the switchCommon
- Faulty transmission control module (TCM)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the code with the switch operated.
- Inspect the downshift switch wiring and connector for damage or corrosion.
- Test the switch for correct open/closed operation with a meter.
- Repair any wiring faults, then replace the switch if it doesn't read correctly.
- If the switch and wiring are good, verify TCM operation.
FAQ
Quick answers
Is it safe to drive with P0816?+
Yes. This is a manual-shift request switch, so the transmission still shifts automatically. Only the manual downshift feature may be affected.
Can I just clear P0816?+
It will return if the switch or wiring is still faulty. It's a low-urgency fix, but the light stays on until the circuit is repaired.
Related codes
Often seen with P0816
Read & clear P0816 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