P0812Reverse Input Circuit
- Generic OBD-II code · Powertrain
- How the car detects it
- P0812 concerns the input 'reverse engaged' at the engine or transmission module – the reverse or back-up lamp switch on a manual gearbox, or the R contact of a selector. Modules check it for open or stuck states and against a second source such as a gear position sensor or the direction from speed sensors. A Honda patent describes this double detection: reverse counts only when switch and gear position sensor agree; if only one reports R, it is a fault and engine speed is limited. No manufacturer document with thresholds is available to us. Back-up lamps, reversing camera or parking aids may fail; on automated manual gearboxes reverse may be blocked. CARB lets such safety and comfort inputs run without the MIL.
- What you may notice
- Back-up lamps never or always on
- Reversing camera or parking aid does not switch on
- Usually no check engine lamp
- Likely causes
- LikelyReverse or back-up lamp switch faulty or misadjusted
- LikelyConnector loose or wire broken (e.g. after clutch work)
- PossibleBack-up lamp circuit fuse blown
- RareGear position sensor reporting the wrong position
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.