Code Definition

P1818 — Transmission Neutral Safety Switch Short Circuit To Battery

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Generic

About P1818

P1818 is a manufacturer-specific powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1818 is stored, the module has detected a short-circuit (voltage pulled to ground or to supply) in the monitored circuit.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1818 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

This DTC is set when the Powertrain Control Module (PCM) or Transmission Control Module (TCM) detects battery voltage on the neutral safety switch signal circuit where it should not be present, indicating a short to battery. The neutral safety switch is designed to provide a ground or specific voltage level when the transmission is in Park or Neutral. If the circuit receives an unintended battery voltage due to a wiring fault or internal switch issue, the PCM identifies this as an abnormal condition and sets P1818.

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