P0813 concerns a signal 'reverse active' that a module puts out – usually the transmission module, on manual cars the engine or body module – for example to the back-up lamp relay, the reversing camera or the body module. Like other driver outputs it is checked by comparing commanded and actual state, which reveals an open circuit or a short. Saab's 2012 transmission module reports a short to positive on its park/neutral output in the same way. No manufacturer document with thresholds for the reverse output is available to us. Back-up lamps, camera or mirror tilt may stop working; driving itself is not affected, and CARB allows such outputs without the MIL.
Medium severity. Can I keep driving?Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
Symptoms
- Back-up lamps not working
- Reversing camera or parking beeper does not activate
- Stored code without driving effects
Most likely causes
- Wire from module to relay or body module open or shorted
- Back-up lamp relay or connected load faulty
- Connector corroded
- Module output stage faulty
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
What each character of P0813 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 8: Transmission
- 13: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0813?
Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
What causes code P0813?
The most common causes are: wire from module to relay or body module open or shorted; back-up lamp relay or connected load faulty; connector corroded.
Related codes
- P0812Reverse Input Circuit
- P0801Reverse Inhibit Control Circuit/Open
- P0817Starter Disable Circuit/Open
- P0705Transmission Range Sensor A Circuit (PRNDL Input)
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.