Code Definition

B2780 — Push Switch / Key Unlock Warning Switch Circuit

System: Body  |  Type: Generic (OBD-II Standard)  |  Make: Lexus

About B2780

B2780 is a generic (obd-ii standard) body diagnostic trouble code recorded for Lexus vehicles. It belongs to the B-prefix family of codes, which covers body, interior, airbag, or comfort-electronics faults.

When B2780 is stored, the module has detected an electrical-circuit fault in the wiring, connector, or driver associated with the named component.

Scanning & clearing: Body (B) codes are often stored in the body control module, airbag module, or climate module. A basic OBD-II tool usually will not read body codes — an enhanced or OEM-level scan tool is typically required.

Because B2780 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The Smart Key ECU monitors the status of the engine start/stop push switch and the key unlock warning switch to determine driver intent and correct key usage conditions. DTC B2780 is stored when the ECU detects an abnormal signal from either switch, such as a signal that is stuck ON or OFF, outside the expected voltage range, or not changing state within a specified time when the switch is operated. This fault indicates that the ECU cannot reliably determine push switch operation or key unlock status, which may inhibit engine starting or generate warning messages.

Quick Facts