Code Definition

B2785 — Ignition switch ON fault

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

About B2785

B2785 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.

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 B2785 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 certification ECU, which manages the Lexus smart key and immobiliser system, monitors the ignition switch ON signal to confirm that the driver has requested ignition power. DTC B2785 is set when the ECU detects an ignition switch ON malfunction, typically when the expected ON signal does not agree with the actual switch state, or when LIN communication between the certification ECU and the related certification components reports an inconsistency three times consecutively. The ignition switch ON signal allows the engine to start and the accessory circuits to operate normally. When this cod...

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