Before starting the vehicle, it’s important to make sure that the transmission is in park/neutral. The transmission control module (TCM) or powertrain control module (PCM) checks the signals from the park/neutral position (PNP) switch to make it happen.
If the PCM detects that the park/neutral safety switch failed to run correctly, its diagnostics will log a P0850 code.
What Does the P0850 Code Mean?
Diagnostic trouble code (DTC) P0850 indicates “Park/Neutral Switch Input Circuit.”
The PNP or range switch keeps the PCM informed about the transmission’s engaged gear. The PNP switch sends a signal that changes according to the shift lever’s location. The PCM will enable or disable the engine and cruise control depending on the signal.
When the transmission is in park or neutral gear, the PNP switch transmits the signal that tells the PCM it can start up the engine.
The PNP switch changes its signal once the transmission shifts out of park or neutral gear. It tells the PCM to stop the engine from starting.
The PCM regularly checks the park/neutral position switch and compares its signal to pre-programmed values in its memory. If the computer doesn’t get the right response, it will set a code P0850.
Note: The definition of code P0850 can differ according to the vehicle manufacturer. Check the appropriate repair manual or repair database for the exact code definition.
What are the Common Causes of a Code P0850?
- Faulty park/neutral safety switch
- Bad PCM or software in need of an update
- Issue with the neutral safety switch wiring
What are the Common Symptoms of a Code P0850?
How to Diagnose the P0850 Code
The P0850 code is a generic code that can show up in many vehicle makes and models. But that doesn’t mean that there’s a universal approach to identifying what triggered it.
If you’re not confident about conducting diagnostic tests on your vehicle, it’s a good idea to bring it to a professional mechanic. Otherwise, you can go ahead and diagnose the issue yourself. To help you get started, here is a video that can give you an idea of what the process might involve:
How to Fix the P0850 Code
Fixing a P0850 code can be tricky if you don’t have the right tools and knowledge to evaluate and replace the park/neutral position switch. So it’s usually best to leave the job to professional technicians.
Do you have the advanced technical knowledge and hands-on experience to test and replace your vehicle’s PNP switch on your own? If so, make sure you refer to a vehicle-specific repair manual or online repair database to ensure you’re following the right steps to resolve the problem.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.
