Battery Temperature Sensor
Powertrain Control Module (PCM) uses Battery Temperature Sensor (BTS) to determine battery temperature and to control battery charging rate. See Fig 1 . Temperature data along with battery voltage data, is used by PCM to vary charging rate. System voltage is higher at colder temperatures and is gradually reduced at warmer temperatures. The PCM sends 5 volts to the sensor and is grounded through the sensor return line. As temperature increases, resistance in the sensor decreases and the detection voltage at the PCM increases. The BTS is also used for OBD-II diagnostics. Certain faults and OBD-II monitors are either enabled or disabled, depending upon BTS input (for example, disable purge and enable leak detection pump and O2 sensor heater tests). Most OBD-II monitors are disabled below 20°F (-6.6°C).