What Causes Volvo's Auto Start-Stop to Stop Working?
3 Answers
Volvo's auto start-stop may pause operation due to the following reasons: Environmental temperature below 0°C or above 40°C, starter battery temperature above 55°C or below 5°C, or engine coolant temperature lower than ambient temperature, or coolant temperature exceeding 100°C. In such cases, wait for the coolant and ambient temperature to rise before restarting the system. Sharp steering wheel turns or driving on steep slopes, or the driver not wearing a seatbelt. In these situations, fasten the seatbelt and move the vehicle to a level surface before restarting the interface. Frequent vehicle starts within a short period activating the electrical thermal protection function. In this case, an electrical thermal protection reset is required, which can be performed at an after-sales service department. Engine auto start-stop is a system that automatically shuts off the engine when the vehicle comes to a temporary stop (e.g., at a red light) during driving. When it's time to move forward again, the system automatically restarts the engine. Its English name is STOP&START, abbreviated as STT.
I've been driving a Volvo XC90 for a while and encountered issues with the auto start-stop not working. Most commonly, when there are significant temperature fluctuations, the system automatically shuts down to protect the engine from extra strain. For instance, in winter when temperatures drop below 5°C or in summer when they exceed 35°C, it tends to pause operation. If the car battery is running low and lacks sufficient power to restart the engine, it can also cause the system to fail. When using the air conditioning or heated seats, the engine needs to keep running to supply cooling or heating, so the start-stop function automatically turns off. Driving habits, such as frequent braking and starting or reversing, can also cause the system to temporarily deactivate to avoid wear and tear. Unfastened seatbelts or slightly open doors will disable it as well. I've tried software updates to fix the issue or visited the dealership to check sensors—usually, it's a minor glitch and nothing to worry about. Keeping an eye on these factors can mostly prevent any impact on driving.
The auto start-stop system relies on the proper collaboration of multiple components. The battery is the core; low charge or aging can cause the system to deem it unsafe, thus preventing operation. Engine temperature is also critical—if the car is cold and hasn't reached operating temperature, the start-stop pauses to ensure proper lubrication. When the air conditioning system has high demand, the engine must run to supply power, so the start-stop automatically deactivates. High vehicle loads, such as using headlights or audio systems, may disable the function if power generation is insufficient. Faulty temperature sensors or alternators may send incorrect signals. Additionally, system software may have bugs requiring an update. The system never activates during reverse gear, a safety feature by design. It's recommended to first use a diagnostic tool to read error codes and identify the root cause. Don’t overlook simple issues, such as the user accidentally pressing the disable button or turning off the function in the settings.
