DTC B1242 Wireless Door Lock Tuner Circuit Malfunction: Description

WARNING: This page is about a different car, the 2008 Lexus IS F. However, it is still accessible from the selected car via links, so may be relevant.

The electrical key antenna and the door control receiver are used to receive electric waves relating to the entry functions of the smart access system with push-button start The certification ECU (smart key ECU assembly) decodes the requested smart access system with push-button start operation by identifying a key code based on electric waves received via the electrical key antenna and the door control receiver
The door control receiver receives a signal from the wireless door control transmitter and sends signals to the main body ECU RH (cowl side junction block RH) through the certification ECU (smart key ECU assembly)
The certification ECU (smart key ECU assembly) then sends a command, according to the requested operation, to each ECU (e g If door lock operation is requested, the ECU sends a door lock command to the main body ECU RH (cowl side junction block RH))

DTC TROUBLE DETECTION CONDITION

DTC No.	DTC Detection Condition	Trouble Area
B1242	The certification ECU (smart key ECU assembly) detects that there is a short in the circuit between terminals RSSI, or between terminals DATA and RDA	Door Control Receiver Wire harness or connector Certification ECU (smart key ECU assembly)