Fault codeP0812

MODERATE

Reverse Input Circuit

What this code means

Reverse Input Circuit.

P0812 is a generic code: it means the same thing on every make. P0812 belongs to family P08xx — Transmission (continued). Its page explains how to read a code and groups all its codes by part.

Type of fault

The control unit has detected an electrical anomaly on this circuit without saying exactly which. Diagnosis starts with a visual check of the wiring and connector, then measuring the component — resistance, supply, ground — with a multimeter.

Gear selector position switches

These switches tell the control units whether the selector is in Park, Neutral, Drive or Reverse. They only allow starting in Park or Neutral, light the reversing lights and lock out reverse while moving on some gearboxes.

What you notice

The engine will not start in Park, reversing lights that do not work, shift indicator wrong on the dashboard.

How to check it

Check the switch on the gearbox, its adjustment with the selector cable and its connector, which is exposed to dirt and water. A slightly misadjusted selector cable is a frequent cause.

Watch it live in Klaro

With an OBD2 adapter plugged in, these live readings show the part at work, when your car reports them:

Vehicle speed

What to do

Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.

Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back. Clearing a fault code yourself →

How to read this code

PPowertrain
0standardised code
8Transmission (continued)
12P0812