What does it mean?
OBD II fault code P0719 is defined as “Torque Converter/Brake Switch B Circuit Low” ( circuit current lower than expected/required], and is set when the Powertrain Control Module detects an abnormal voltage or resistance in the “B” circuit of the brake light switch. The “B” refers to the circuit that controls the brake lamps, which is also the circuit that deactivates the cruise control system (where fitted), and the torque converter lock-up mechanism on vehicles with lockable torque converters.
When the brake controller, such as the ABS system receives a signal from the brake lamp circuit, but the Powertrain Control Module detects a current or resistance that does not correspond to a specified value, code P0719 is stored, and the Check Engine warning light may, or may not be illuminated. The code-setting parameters, as well as the number of fault cycles required to illuminate warning lights may vary from vehicle to vehicle.
Data between the various control modules involved in generating, and storing code P0719 is transmitted via the CAN Bus system. The image below shows the typical location of a brake light switch, which is more often than not the root cause of code P0719 when it fails, or works itself out of optimal adjustment. Note that there are considerable differences in the design, location, operation, and appearance of brake light switches between vehicles.