On vehicles equipped with an automatic transmission and four-wheel-drive, the park/neutral switch tells the computer that the transmission has been placed in either Park or Neutral. If the ECU has detected an abnormal voltage signal on this switch’s circuit, a P0850 DTC will be set.
How Serious is the Code?
A P0850 diagnostic trouble code means that the computer is not sure whether or not the transmission has been shifted into a neutral gear. This can affect the drivability, and prevent the four-wheel-drive system from engaging.
Symptoms of a P0850 include:
- Cannot engage four-wheel-drive
- Harsh shifts
- Failure to shift gears
- Damaged wiring and/or corroded connectors
- Improperly installed sensor retaining bolts
- Faulty park/neutral switch / sensor
- Transfer case range sensor needs to be adjusted
- Failed transmission range sensor
How to Diagnose the Code?
The first step to diagnosing a P0850 OBDII trouble code, carefully check the condition of the wiring and connectors. Next, the park/neutral switch will need to be tested to ensure that it is properly grounded and the voltage readings are consistent with the manufacturer’s specification. If no problems are found by this point, then the transfer case range sensor and transmission range sensor should be tested.
What Repairs Will Fix P0850?
- Repair or replace damaged wiring and connectors
- Replace Park/Neutral switch
- Adjust transfer case range sensor
- Replace transmission range sensor
- Install new sensor retaining bolts
- P0851 – Park/Neutral Switch Input Circuit Low
P0852 – Park/Neutral Switch Input Circuit High
P0853 – Drive Switch Input Circuit
P0854 – Drive Switch Input Circuit Low