The steering wheel switches can be used to operate a connected cellular phone.
Operating a telephone using the steering wheel switches

Calling the message sender
Bluetooth® phone
settingsTC and CG Terminal Circuit
DESCRIPTION
Connecting terminals TC and CG of the DLC3 causes the system to enter the
self-diagnostic mode. If a
malfunction is present, DTCs will be output.
HINT:
When a particular warning light remains blinking, a ground short in the wiring
of terminal TC of the DLC3
or an internal ground ...
Terminals of ECU
1. CLEARANCE WARNING ECU
*1: with Front Clearance Sonar
2. AIR CONDITIONER AMPLIFIER ASSEMBLY
*1: with Front Clearance Sonar
*2: Manual A/C
*3: Auto A/C
Reference: waveform 1
HINT:
Terminal: CBZ - E, BBZ - E, Z- - Body ground
Gauge set: 2 ...
Precaution
1. PRECAUTION FOR VEHICLE WITH SRS AIRBAG
AND SEAT BELT PRETENSIONER
Some operations in this section may affect SRS
airbag system. Before performing the corresponding
operations, please read the NOTICE of the SRS
airbag for the proper operations.
COMPONENTS
...