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Battery Temperature Sensor

The battery temperature sensor is actually inside the power module (or SMEC). It measures the air temperature as it flows through the power module, using the temperature to calculate the intake air density and target charging system voltage.

The battery temperature sensor reacts to different temperatures by producing a voltage between .04 volts and 4.96 volts DC, based on an input voltage of 5 volts DC. Because the logic module is so close to the battery, these readings can be used to estimate the temperature of the battery itself. Knowing the temperature of the battery is important because batteries are sensitive to heat, and the logic module will reduce the power sent to the battery by the alternator to prevent “cooking the battery.”

If the logic module detects a voltage outside the normal range (0.04 to 4.96 volts), it triggers a code 44 and the charging rate is set to 14.0 volts as a “safe” option.  If the output of the sensor returns to the normal range, the logic module will return to normal operation and it will use the output from the sensor to adjust charging rates.

LINKS: Code 44 | Charging system and battery diagnosis

