P0850: Park/Neutral Switch Input Circuit
What to do
The engine may refuse to crank, or crank only in one selector position. Ask whether a separate park/neutral switch is fitted as well as the range sensor — on many vehicles they are two parts, and this code names the simpler and cheaper one.
What this code means
The signal telling the module the transmission is in park or neutral is missing or implausible.
On many vehicles this is a simpler and separate input from the full transmission range sensor, and that separation is deliberate rather than redundant clutter. The starter interlock is a safety function, and hanging it on a multi-position sensor that must resolve six or seven distinct positions puts a complex part in a critical path. A plain switch that closes in park or neutral and does nothing else is easier to trust, easier to test, and fails in more predictable ways.
So where both this and a range sensor code are stored, they are describing two different parts and both may need attention. Where only this one is stored, the range sensor is probably fine and the simple switch is the whole problem — which is the cheaper of the two outcomes.
Likely causes
Start here
- Faulty park neutral switch · moderate
- Misadjusted transmission range sensor · moderate
- Corroded or loose connector · easy
Less common
- Open circuit in switch wiring · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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- The car — make, model, year and engine. The same fault behaves differently on each.
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