P0812 Code: Reverse Input Circuit — Causes & Fix
P0812 means a fault in the reverse input circuit — the signal that tells modules the transmission is (or should be) in reverse.
- Applies to
- All OBD-II vehicles (any make or model)
- Est. repair cost
- $30 – $400
- Time to fix
- 1–4 hours
What it means
Causes include a failed reverse/range switch, wiring faults, or a connector problem. P0812 is a generic OBD-II code defined in the SAE J2012 standard, so it applies to virtually any 1996-or-newer OBD-II vehicle regardless of make. Fix the underlying fault, then clear the code with an OBD-II scan tool — it will return if the problem isn't resolved.
Symptoms
- Check engine light on
- Reverse lights not working
- Possible reverse-gear or shift concerns
How to fix it
- 1
Check the reverse/range switch
1. Confirm the reverse lights and switch operation. 2. Inspect wiring.
- 2
Repair/replace
1. Replace a faulty switch or repair wiring, then clear the code.
Frequently asked questions
Are my reverse lights related to P0812?
Yes — the reverse input often drives the reverse lights, so a fault can turn them off and set this code.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.