Code Definition

P1520 — Stop Lamp Switch Signal

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

About P1520

P1520 is a manufacturer-specific powertrain diagnostic trouble code recorded for Toyota vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

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.

P1520 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 fault code sets when the Engine Control Module (ECM) detects an abnormal signal from the stop lamp (brake light) switch, which reports brake pedal application. The ECM uses this input for functions such as cruise control cancellation, idle control, and transmission and torque converter control. If the signal is missing, stuck on or off, or inconsistent with vehicle behaviour, such as showing the brake applied while driving steadily, the ECM sets this code. The driver may notice cruise control that will not engage, brake lights that stay on or do not work, and a check engine light.

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