DTC B1242: Wireless Door Lock Tuner Circuit Malfunction [06/2018 - ]: Description

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2024 Lexus ES 300h, 2023 Lexus ES 300h, 2022 Lexus ES 300h, 2021 Lexus ES 300h, and 2020 Lexus ES 300h. However, it is still accessible from the selected car via links, so may be relevant.

The electrical key and tire pressure monitoring system receiver assembly is used to receive radio waves related to the entry functions of the electrical key transmitter sub-assembly. The certification ECU (smart key ECU assembly) decodes the requested electrical key transmitter sub-assembly operation by identifying a key code based on the radio waves received via the electrical key and tire pressure monitoring system receiver assembly. The electrical key and tire pressure monitoring system receiver assembly receives a signal from the electrical key transmitter sub-assembly and sends signals to the main body ECU (multiplex network body ECU) through the certification ECU (smart key ECU assembly). (ex. If a door lock operation is requested, the certification ECU (smart key ECU assembly) sends a door lock command to the main body ECU (multiplex network body ECU)).

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
B1242	Wireless Door Lock Tuner Circuit Malfunction	Short to ground in RDAM terminal circuit between the certification ECU (smart key ECU assembly) and electrical key and tire pressure monitoring system receiver assembly. Short to ground in RDAM terminal circuit when voltage (5 V) is not being output from terminal RCO	Wire harness or connector Electrical key and tire pressure monitoring system receiver assembly Certification ECU (smart key ECU assembly)