The quick answer is no, not easily, and definitely not without specialized manufacturer tools.
Delving deeper, the possibility becomes a very complex maybe. In modern vehicles, the body control module (BCM) is the central command for nearly all external and internal lighting, including turn signals. Switches throughout your car communicate with the BCM, offering incredible flexibility in lighting control. For instance, if you accidentally leave your headlights or interior lights on, the BCM intelligently intervenes, shutting them off after a set period to prevent battery drain.
Turn signals in newer cars operate differently from older models. Traditional turn signals used a thermal flasher unit. When activated, electricity flowed through a spring, heating it up. This heat caused the spring to expand and break the circuit, and as it cooled, the circuit would remake, creating the familiar clicking sound and flashing light. Modern vehicles, however, use software within the BCM to manage the turn signals, and that clicking sound you hear is often artificially generated by a speaker within the instrument cluster.
While it’s technically feasible to control lights, including turn signals, via the OBD2 port, it requires sending a specific “input/output control” diagnostic command. This command, defined in the ISO-14229 Unified Diagnostic Services standard, needs the correct identification (ID) code for the specific light you wish to manipulate. The major hurdle is that these IDs are not universal; they are unique to each vehicle manufacturer. This crucial information is typically exclusive to the manufacturer’s proprietary diagnostic software and hardware.
One theoretical, albeit highly impractical, approach would be to attempt to “brute force” these IDs. This would involve systematically sending input/output control commands for a vast range of potential IDs within the system supplier-specific range (potentially hundreds of IDs). Such an endeavor would demand substantial expertise, time, and dedicated effort, making it far from a realistic solution for most individuals wanting to control their Obd2 Turn Signal functions.
