P0812 Code: Meaning, Symptoms, Causes & Fix

Overview

P0812 is triggered when monitoring logic identifies an issue with Reverse Input Circuit affecting powertrain controls.

Symptoms

reduced performance
increased fuel use
check engine light

Common causes

Open circuit in wiring affecting reverse input circuit
Broken terminal inside harness
Connector pin damage/corrosion or harness stress near related components

How to diagnose P0812

Confirm P0812 and capture freeze-frame data with a professional scan tool.
Inspect wiring, connectors, and grounds related to reverse input circuit for obvious defects.
Use a continuity test from module pin to component to identify opens/high resistance.
Check for related DTCs to identify the root-cause chain before replacing parts.
After repair, clear codes and confirm readiness monitors complete without recurrence.

Severity of code P0812

Moderate: This code is moderate severity: the vehicle may still operate, but fault progression can increase repair cost over time.

Can you drive with P0812?

Most vehicles can be driven short-term with P0812, but postpone heavy load/highway driving until repaired.

If the warning lamp is flashing or drivability/safety is affected, avoid driving and diagnose immediately.

How to fix it (step-by-step)

Repair obvious wiring/connector faults first to prevent repeat parts replacement.
Address the root fault mode (open) in the reverse input circuit circuit/system.
Apply the required relearn/adaptation procedure if specified by service information.
Road-test and verify P0812 remains cleared under the conditions that originally set the code.

Fix options

Repair open circuit and secure connector lock.
Clear corrosion and protect terminals.
Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$200-$900

Common mistakes when diagnosing P0812

Replacing parts without verifying voltage, ground, and signal integrity first.
Ignoring related stored/pending codes that indicate upstream faults.
Skipping post-repair verification drive cycle and readiness checks.

P0812 in common vehicles

P0812 appears across makes such as Mazda, Subaru, Lexus, Jeep. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.

Frequently asked questions

What causes P0812?

P0812 is commonly set by open faults affecting reverse input circuit.

How much does it cost to fix P0812?

For P0812, repair costs are typically $200-$900 depending on exact root cause, labor rates, and part quality.

Can I clear P0812 without repair?

You can clear P0812 temporarily, but the code usually returns until the underlying fault is corrected.