P0850: Park/Neutral Switch Input Circuit

What does P0850 mean?

The park/neutral input tells the engine control module whether the automatic is in P or N, or a manual gearbox in neutral. It releases the starter, prepares idle control for the load of an engaged gear and enables cruise control and other monitors. All documented makers check it for plausibility against driving state or a second source such as the gearbox module. On GM's 6T70 and Subaru the switch pulls the line to ground in P/N. P0850 is the general fault. Ford's 2023 diesels check the switch for plausibility at start-up and set the code after 1 s. On GM's 6T70, as in the Saab 9-4X, the module sees P/N while the range switch reports a gear for 0.2 s above 10 km/h and 75 Nm, type C without MIL; it then uses the range switch for start release.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Engine does not crank in P or N
• Engine cranks in a drive range (safety risk)
• Rough or wrong idle
• Cruise control not working

Common causes

• High Range or inhibitor switch faulty or misadjusted
• Medium Selector cable misadjusted or stretched
• Medium Wiring or connector between switch, gearbox module and engine module
• Low Module input or software

Likelihood is a general estimate across vehicles; your make and model may differ.