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P0850 OBD-II Trouble Code: Park / Neutral Switch Input Circuit

Check Engine Light

P0850 code definition

If the PCM has stored the P0850 code, it means that the input circuit which measures the function of the park/neutral switch has given an abnormal voltage reading.

What the P0850 code means

If the vehicle is put into park or neutral, voltage readings are sent to the PCM from a variety of sensors and components. This data helps the PCM ensure that park or neutral was achieved, and that the vehicle is operating correctly. If the voltage reading from the input circuit on the park/neutral switch does not match the manufacturer’s specifications, the PCM will store the P0850 code. This code is only applicable in vehicles with both an automatic transmission, and four-wheel-drive capability.

What causes the P0850 code?

In the majority of instances, the P0850 code is caused by a misadjusted transfer case range sensor. This could have been improperly installed during a previous repair.

Other causes may include:

  • Faulty park/neutral switch
  • Open or shorted park/neutral switch harness
  • Poor electrical connection in the park/neutral switch circuit
  • Defective range sensor
  • Damaged wiring or other electrical components
  • Improperly installed sensor retaining bolts
  • Excessively corroded sensor connector

What are the symptoms of the P0850 code?

In addition to the illumination of the Check Engine lamp, vehicle owners may observe symptoms such as the inability to engage the four-wheel-drive, harsh shifting or complete failure to shift, and a decrease in fuel efficiency.

How does a mechanic diagnose the P0850 code?

The first step is to verify the code with an OBD-II scanner. Once this step has been completed, the mechanic should begin with a visual inspection of all electrical components, including wiring and connectors. Repair or replace any parts as necessary, and then clear the code from the PCM and retest the system. If the code reappears, the next step is to check the battery voltage and ground signals at the park/neutral switch.

Throughout the diagnostic process, the mechanic should compare readings to the manufacturer’s specifications. If the readings are within the acceptable range, then suspect the sensor itself is bad; if the readings are not within the acceptable range, then other repairs will have to be attempted. Always remember to clear the code and retest the system after each potential repair, to ensure that the correct repair is pinpointed and time is not wasted on further repairs.

Common mistakes when diagnosing the P0850 code

The most common misdiagnosis is to blame a faulty transfer case range sensor, when in fact the part was not faulty, but simply misadjusted.

How serious is the P0850 code?

Because this code directly relates to the vehicle’s drivability, it is considered an important matter that should be addressed right away. Allowing the P0850 code to remain unrepaired could create unsafe driving conditions, and cause larger and more expensive repairs to be necessary. When the P0850 code is detected, it is best to have an auto service technician address the issue right away.

What repairs can fix the P0850 code?

There are many ways that a technician can address a P0850 code detection. They include:

  • Adjust transfer case range sensor
  • Replace faulty park/neutral switch
  • Repair open or shorted park/neutral switch harness
  • Repair poor electrical connection in the park/neutral switch circuit
  • Replace defective range sensor
  • Replace damaged wiring or other electrical components
  • Properly install sensor retaining bolts
  • Replace excessively corroded sensor connector

Need help with a P0850 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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