P0143 - O2 Sensor Circuit Low Voltage (Bank 1, Sensor 3)

P0143 is set when the Engine Control Module (ECM) detects that the signal voltage from the post-catalytic converter Oxygen (O2) sensor (Bank 1, Sensor 3) is staying below a calibrated threshold (typically below 0.2V) for a specified duration. This sensor's primary role is monitoring the catalytic converter's storage capacity and efficiency. A steady low voltage reading usually indicates either a lean exhaust condition or an electrical issue such as a short to ground or an open circuit in the signal return line.