Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Battery Temperature Sensor (Replaced By Software Starting From Structure Week 200605)
The battery temperature sensor checks the temperature of the battery. To charge the battery optimally the central electronic module (CEM) calculates the output voltage from the generator (GEN) using the temperature of the battery.
The sensor is a negative temperature coefficient (NTC) type which is supplied with power from the control module (signal) and is grounded in the control module.
The resistance of the sensor changes with the temperature of the battery. This alters the signal to the central electronic module (CEM). At:
- +20 °C the resistance is approximately 3.5 kΩ
- 0 °C the resistance is approximately 9.4 kΩ
- -20 °C the resistance is approximately 28.6 kΩ.
The lower the temperature the higher the resistance (high voltage). A high temperature results in low resistance (low voltage).
The battery temperature sensor is in the bottom of the battery box. The sensor is directly connected to the central electronic module (CEM).
The central electronic module (CEM) has diagnostics for the battery temperature sensor. The temperature can be read off using VIDA (Volvo scan tool).
From structure week 200605, the battery temperature sensor has been replaced by software. Battery temperature is then calculated from four input signals: outside temperature, engine temperature, vehicle speed and power supply status. The function is diagnosed by the central electronic module (CEM). Temperature can be read off using VIDA (Volvo scan tool).
If the central electronic module (CEM) detects a fault in the sensor or the calculation function, a substitute value of +55 °C is used. This generates a fixed generator output voltage of 13.5 V.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.