P0851 - OBD II Trouble Code

Our automotive experts have put together the following information about the P0851 diagnostic trouble code. We've provided the common symptoms that occur when this code is set along with the frequent repairs that address the issues related to the P0851 code.

OBD II Fault Code

• OBD II P0851

OBD-II Code Engine may not start is defined as a Park/Neutral Switch Input Circuit Low

The engine computer (PCM) needs to know when the transmission is in Park/Neutral, as this is required before the vehicle can safely be started. The PCM depends on the park/neutral safety switch to communicate when the transmission is in Park/Neutral. If the Park/Neutral Safety Switch fails to operate properly, code P0851 will be set. The engine may be disabled from starting.

Engine may not start Symptoms

• Engine may not start

Common Problems That Trigger the P0851 Code

• Neutral safety switch failure
• Powertrain Control Module (PCM) failure
• Wiring issue