P0813 Reverse Output Circuit

P0813 indicates a reverse output circuit fault. The module cannot correctly drive or monitor the circuit used for reverse-related output control.

Code details

Generic OBD-II · P0

System: Transmission
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not assume the reverse switch is bad if the code identifies an output circuit.

Symptoms of P0813

Harsh, delayed, or slipping shifts, or being stuck in one gear.
Check-engine light, sometimes with limp-home mode.
Flaring RPM or a shudder under load.

Common causes of P0813

Low or degraded transmission fluid.
A failing speed sensor, shift solenoid, or pressure-control circuit.
Wiring, connector, or internal hydraulic/mechanical faults.

Useful checks before replacing parts

Check reverse output command, circuit voltage, load condition, fuse feed, ground path, and the device controlled by the output.
Inspect wiring to reverse lamps, relay, camera trigger, transmission control device, or other vehicle-specific reverse output loads.
Review module data to see whether the reverse input is correct before diagnosing the output side of the circuit.

Related OBD-II codes

These nearby transmission entries can help compare wording and pin down the fault area.