The PCM incorporates a Battery Temperature Sensor (BTS) on its circuit board.The PCM uses the temperature of the battery area to control the charge rate. The signal is used to regulate the system voltage. The system voltage is higher at cold temperatures and is gradually reduced as temperature around the battery increases.The function of the BTS is to enable control of the generator output based upon ambient temperature. As temperature increases, the charging rate should decrease. As temperature decreases, the charging rate should increase. The sensor functions similar to the ECT sensor with one major difference, the ambient sensor does not have a dual temperature range program. The PCM maintains the maximum output of the generator by monitoring battery voltage and controlling battery voltage to a range of 13.5 - 14.7 volts.
You may need to have the PCM re-programmed to re-calibrate the Battery Temp Sensor.