P0813 OBD-II Trouble Code: Reverse Output Circuit Malfunction

P0813 code definition

P0813 is the fault code for the Reverse Output Circuit.

What the P0813 code means

This is the generic OBD-II fault code indicating an issue within the reverse output circuit. When you shift your vehicle into reverse, the PCM (powertrain control module) monitors the voltage signal sent from the reverse input switch. If the PCM detects a signal outside of the expected range, the P0813 will set, indicating a malfunction somewhere within the circuit.

What causes the P0813 code?

A few things may trigger this code to be stored in the vehicle’s computer:

• A defective reverse input switch (the most common cause)
• A short or open in the wiring and/or connectors associated with the reverse input switch
• Very rarely, a faulty PCM

What are the symptoms of the P0813 code?

A problem in the reverse output circuit may cause the Check Engine light to illuminate. In addition to the CEL and the stored trouble code, the back-up lamps may fail to work.

How does a mechanic diagnose the P0813 code?

Steps that your technician may carry out in order to diagnose code P0813 include:

• Hooking the vehicle up to an OBD-II scanner in order to verify the stored code and check for any other trouble codes that may be present
• Recording the information on these codes, such as the time, frequency, and order in which they occurred, and capturing the freeze frame data
• Diagnosing and repairing any other issues that occurred prior to the reverse output circuit malfunction
• Clearing the data from the vehicle’s computer and retesting the vehicle to make sure the same code returns
• Performing a visual inspection of the wiring and connectors to check for corrosion or loose connections
• Checking for voltage on the switch’s input side
• Checking for continuity between the fuse and the reverse input switches input circuit
• With the vehicle in reverse, checking for voltage on the output side of the switch
• Checking continuity and resistance between the reverse input switch and the PCM

Related control modules should be disconnected from the PCM before testing the circuitry. Disconnecting any related control modules can prevent damage to these expensive components and having to reprogram the vehicle’s computer.

Common mistakes when diagnosing the P0813 code

If this fault has caused back-up lamp failure, people will often assumed the back-up lamp bulbs are to blame, when in fact there is a short in the wiring, bad connectors, or a defective reverse input switch.

How serious is the P0813 code?

While not as serious as other codes which affect the vehicle’s ability to run, this code should be addressed in a timely manner due to the possibility of back-up lamp failure. Driving without back-up lamps could cause a dangerous situation if other drivers can’t tell that you’re backing up.

What repairs can fix the P0813 code?

Repairing a faulty reverse output circuit may involve one or more of the following:

• Repair or replacement of corroded or faulty wiring or connectors
• Reverse input switch replacement
• Rarely, PCM replacement

Additional comments for consideration regarding the P0813 code

The manufacturer’s wiring diagram specific to your vehicle should be used to ensure that all of the correct circuits are tested. On vehicles with automatic transmissions, the reverse input switch is often part of a manual lever position sensor or neutral safety switch. On vehicles with a manual transmission, the switch may be threaded onto the transmission housing near the gear shifter. This diagnosis may involve testing with a code reader and a digital volt/ohmmeter. When considering whether the attempt the repair on your own, keep in mind that your professional mechanic has tools that provide more detailed information than those designed for driveway use. If you have any doubts about how to fix a P0813 code, consult your qualified professional.

Need help with a P0813 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.