P0813: Reverse Output Circuit

What it means

A fault was detected in the reverse output circuit. The code does not establish which components that circuit controls.

At a glance

• Usually lights the check-engine light

How it works

The reverse output circuit carries a module-controlled signal for a reverse-related output. The control module monitors the output circuit and sets P0813 when it detects an electrical fault. The code does not identify which device the circuit controls or whether the fault is in the wiring, output driver, or device.

Common causes

Most likely first.

1. Open circuit in reverse output wiring
2. Short to ground or power in the output circuit
3. Loose or corroded connector
4. Faulty output driver or controlled device
5. Control module circuit fault

Symptoms

• Check engine or transmission warning light on
• Harsh, delayed, or missing shifts
• Possible limp mode (locked in one gear)
• Slipping or shuddering during gear changes

How to diagnose it

1. Record freeze-frame data and scan transmission live data for reverse output command and related codes to establish when the circuit fault occurs.
2. Check whether the reverse-related function responds when reverse is selected, while keeping the vehicle secured and following safe operating precautions.
3. Inspect the output circuit harness and connector for loose pins, corrosion, chafing, or damage near the controlled device.
4. Test the output wire for opens and shorts to ground or power, then test the connected device according to the manufacturer's procedure.
5. If wiring and device tests pass, check module power, grounds, connector condition, and output-driver operation.

Common fixes

• Repair an open or shorted reverse output wire.
• Repair loose, corroded, or damaged connector terminals.
• Replace the controlled device if it fails its manufacturer's test.
• Repair a module output fault only after confirming the circuit and device are sound.

Can I keep driving?

If reverse or another affected function behaves unpredictably, avoid driving in areas where you need to rely on it and have the vehicle checked promptly. Stop if gear selection becomes unreliable or the transmission loses drive.