Does the Auto Start-Stop Function Cause the Engine to Shut Off When Shifting to P Gear?
4 Answers
It may be caused by the auto start-stop function being activated when shifting to P gear and pressing the brake pedal, leading to automatic engine shutdown. Working principle of the start-stop system: When the vehicle stops moving due to traffic congestion or at an intersection, the driver presses the brake pedal and shifts to neutral. Once these three conditions are met, the engine automatically stops running. Operating state of the start-stop system: The start-stop system is translated as the Start-Stop system in English; when the vehicle is in a stopped state (not in park), the engine will pause operation (instead of maintaining traditional idle speed). During this pause, the lubricating oil inside the engine continues to circulate, ensuring internal lubrication.
The other day when I was driving to pick up a friend, I noticed the engine shut off by itself while waiting at an intersection with the gear in P position. This is actually the auto start-stop system functioning normally, and it's not related to being in P gear. I specifically consulted a friend at the repair shop - this system triggers engine shutdown whenever the vehicle comes to a complete stop, whether by braking or shifting to P gear. Especially with the AC running in hot weather recently, I've observed that when start-stop activates in P gear, the AC temporarily switches to fan-only mode. However, it's worth noting that repeated P gear shifts causing engine shutdowns can be quite annoying when searching for parking spots - in such situations, I simply turn off the start-stop function. Additionally, if the battery charge is insufficient or the outside temperature is too low, the start-stop system may automatically suspend operation, which are all normal protective mechanisms.
I've studied the auto start-stop logic of many cars, and shutting off the engine in P gear is completely a normal system response. This system is actually quite intelligent - it triggers engine shutdown in any gear position after determining the vehicle is completely stationary via speed sensors. However, some models do have slightly different designs, such as disabling start-stop when in P gear on slopes to prevent dangerous rolling. Through practice with my own car, I've found that when there's high demand for air conditioning cooling, the system prioritizes maintaining engine operation. Frequent start-stops do slightly increase the starter motor's workload, but modern vehicles have reinforced these components, making it generally not a major concern. I recommend regularly checking battery condition, as an aging battery can affect start-stop functionality.
I really like the auto start-stop feature. Every time I shift to P at a red light and the engine shuts off, it saves some fuel. This is a common phenomenon where the system automatically shuts down to save energy when it detects the vehicle is stationary. However, I've noticed that on extremely hot days, high AC demand often prevents the start-stop from working. Actually, start-stop activation isn't strongly related to gear position - it mainly depends on whether the vehicle has come to a complete stop. If shifting to P doesn't shut off the engine, it might be due to insufficient battery charge or the system detecting other abnormalities. When waiting for long periods, I always consciously shift to P to let the start-stop work, saving fuel while keeping things quiet.
