Code Definition

B2798 — Immobiliser system communication problem

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

About B2798

B2798 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 B2798 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

DTC B2798 is set by the ECM when it detects a communication malfunction in the Lexus immobiliser system, specifically a failure to correctly exchange or agree the encrypted authentication code with the transponder key ECU. Unlike a complete loss of communication, this code typically means the two modules are linked but cannot complete the secured code exchange, which often follows incorrect registration after a module replacement or a fault on the data line. The immobiliser will not authorise the ECM to start the engine until the encrypted handshake succeeds. When this code is set the engine c...

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