The P0851 trouble code indicates that there is a low input signal from the park or neutral switch circuit. Here’s what you should know:
P0851 Park/Neutral Switch Input Circuit Low
Code symptoms P0851.
1. Difficulty starting the vehicle.
2. Inability to shift out of park or neutral.
3. Engine stalling when shifting gears.
4. Illumination of the Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL) on the dashboard.
Causes of the code P0851.
1. Faulty park or neutral switch.
2. Damaged or corroded wiring or connectors in the switch circuit.
3. Misalignment of the park or neutral switch.
4. Issues with the transmission range sensor.
5. Faulty transmission control module (TCM).
Code Solutions P0851.
1. Replace the park or neutral switch if it’s found to be faulty.
2. Repair or replace any damaged wiring or connectors in the switch circuit.
3. Adjust or realign the park or neutral switch if necessary.
4. Ensure proper installation of the park or neutral switch and secure any wiring harnesses.
5. Reset the fault codes and test drive the vehicle to verify that the issue has been resolved.