The P0851: Park/Neutral Switch Input Circuit Low refers to a condition where the park/neutral switch input circuit is detecting lower-than-expected voltage. This can cause issues with starting the vehicle or affect its ability to shift correctly. The problem could be due to a faulty switch, wiring issues, or a malfunction in the transmission control module (TCM).
P0851 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P0851: Park/Neutral Switch Input Circuit Low |
| Is it serious? | Yes, this may prevent the vehicle from starting or cause transmission shifting problems. |
| Possible causes | – Low voltage in the park/neutral switch input circuit – Faulty switch or wiring – Faulty transmission control module (TCM) |
| How to diagnose? | – Test the circuit for low voltage – Inspect wiring and connectors – Replace faulty components if needed |
P0851 Meaning
The P0851: Park/Neutral Switch Input Circuit Low code indicates that the voltage in the input circuit of the park/neutral switch is below the specified range. This low voltage can prevent the vehicle from detecting that it is in park or neutral, leading to issues with starting or shifting the vehicle.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to check for any additional related codes to gain further insights into the issue. | OBD-II Scanner |
| Inspect Park/Neutral Switch | Visually inspect the park/neutral switch for signs of damage, wear, or misalignment. | Flashlight, Safety Gloves |
| Test the Circuit for Low Voltage | Use a multimeter to measure the voltage in the park/neutral switch input circuit and ensure it falls within manufacturer specifications. | Multimeter |
| Check Wiring and Connectors | Inspect the wiring and connectors for damage, corrosion, or loose connections that could cause low voltage in the circuit. | Flashlight, Multimeter |
| Replace Faulty Components | If the park/neutral switch, wiring, or connectors are faulty, replace the affected components to restore proper functionality. | Replacement Parts, Basic Tools |
| Clear the Code and Test Drive | After repairs, clear the code using an OBD-II scanner and take the vehicle for a test drive to ensure proper operation. | OBD-II Scanner, Vehicle Owner’s Manual |
| Recheck for Codes | After the test drive, re-scan the system to confirm that the P0851 code does not return. | OBD-II Scanner |
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I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko