P0855
Drive Switch Input Circuit High
Transmission / gear selector
Generic OBD-II
Medium
What it means
P0855 means the transmission control module detects a higher-than-expected voltage on the drive switch input, the circuit that tells it when Drive is selected. A stuck-high signal can leave the module unsure of the gear request, causing trouble engaging Drive or erratic shifting. The engine still starts — this is a selector-circuit fault, not an engine problem.
Medium
Can I keep driving? The engine starts, but the transmission may not recognize Drive or may hold a gear — have it checked before relying on the car.
Common symptoms
What you'll notice
- Check-engine light on
- Difficulty engaging or selecting the Drive gear
- Transmission behaves erratically or holds a single gear
- Drive position may not register
Common causes
Most likely first
- Wiring or connector fault in the drive switch input circuit (shorted high)Likely
- Faulty drive selector switchCommon
- Loose or corroded connectors in the transmission harnessCommon
- Failed transmission control module (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and inspect the drive switch connector for corrosion, damage, or a pin shorted to voltage.
- Measure the drive switch input circuit for a persistent high voltage and check for a short to power.
- Verify the switch's ground and signal circuits with a multimeter as the selector is operated.
- Replace the drive switch if it signals incorrectly with wiring confirmed good. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0855?+
The engine runs, but if the transmission won't recognize Drive you could be stranded, so get it diagnosed before depending on the vehicle.
Can I just clear P0855?+
It will clear, but the high-voltage condition returns until the shorted wiring or faulty switch is repaired.
Related codes
Often seen with P0855
Read & clear P0855 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