P0812: Reverse Input Circuit OBD-II Trouble Code

A P0812 OBD-II code indicates an issue with the vehicle’s reverse input circuit, which may cause the reverse lights to work intermittently or not at all.
The purpose of the reverse input sensor is to tell the PCM that the transmission is in reverse, and when it’s detected that the signal is lost or receiving incorrect voltage, it will trigger a P0812 code.

How Serious is a P0812 Code?

A P0812 diagnostic trouble code isn’t really going to affect the performance of your vehicle. But it can affect the safety of your vehicle if the reverse lights stop working.

P0812 Symptoms

Common symptoms of a P0812 include:

  • Reverse lights stop working – Typically the P0812 will not trigger a check engine light (CEL) unless it’s a repeated issue.  The vehicle needs to see that the signal is being lost first before setting off a warning.

Causes of P0812 Code

  • Damaged wiring/connectors
  • Blown fuse
  • Faulty reverse input switch

How to Diagnose A P0812 Code

In order to properly diagnose a P0812 code, the first things to dig into are doing a thorough inspecting of all related wiring and connectors. Depending on the condition of the condition of the existing wiring or plugs, it could be a relatively easy (in a general sense) fix that’s not too serious.

Once all wiring and connections are checked out, it would be best to move on to the reverse input switch itself.  At the same time as testing the reverse input switch, the associated fuses and bulbs should be looked at as well.  This is a rather simple procedure, and you should consult your owner’s manual or repair manual for more information.


What Repairs Will Fix P0812?

  • Repair or replacement of  faulty wiring and or connectors
  • Replace reverse input switch
  • Replace blown fuses or bulbs