Definition of Code P0850
If the PCM has stored code P0850, it means that the input circuit measuring the function of the park/neutral switch has provided an abnormal voltage reading.
What does code P0850 mean
When 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 has been engaged and that the vehicle is operating correctly. If the voltage reading from the park/neutral switch input circuit does not match the manufacturer’s specifications, the PCM will store code P0850. This code only applies to vehicles equipped with both an automatic transmission and a four-wheel drive system.
What causes code P0850?
In the majority of cases, code P0850 is caused by a misadjusted transfer case range sensor. This may 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
- Faulty range sensor
- Damaged wiring or other electrical components
- Improperly installed sensor retaining bolts
- Excessively corroded sensor connector
What are the symptoms of code P0850?
In addition to the Check Engine light illuminating, vehicle owners may observe symptoms such as the inability to engage four-wheel drive, harsh shifting or complete failure to shift, and decreased fuel economy.
How does a mechanic diagnose code P0850?
The first step is to verify the code with an OBD-II scanner. Once that is done, the mechanic should begin with a visual inspection of all electrical components, including wiring and connectors. Repair or replace parts as necessary, then clear the code from the PCM and retest the system. If the code returns, the next step is to check 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 faulty; if the readings are not within the acceptable range, further repairs will need to be attempted. Remember to clear the code and retest the system after each potential repair, to ensure the correct fix is identified and you are not wasting time performing unnecessary repairs.
Common mistakes when diagnosing code P0850
The most common diagnostic error is blaming a faulty transfer case range sensor, when in fact the part was not defective, but simply misadjusted.
How severe is code P0850?
Since this code relates directly to the vehicle’s drivability, it is considered a significant issue that must be addressed immediately. Failure to repair code P0850 could create dangerous driving conditions and lead to larger, more costly repairs. When code P0850 is detected, it is best to have an automotive technician address the problem right away.
What repairs can fix code P0850?
There are many ways for a technician to address a code P0850 detection. They include:
- Adjusting the transfer case range sensor
- Replacing the faulty park/neutral switch
- Repairing the open or shorted park/neutral switch harness
- Repairing a poor electrical connection in the park/neutral switch circuit
- Replacing the faulty range sensor
- Replacing damaged wiring or other electrical components
- Properly installing the sensor retaining bolts
- Replacing the excessively corroded sensor connector