Torque Shop: i-stop symbol lights up when car is moving and goes off when it stops

In newer Mazda cars, the yellow i-stop warning indicates that the stop-start function is deactivated. PHOTO: ST FILE

I am driving a six-year-old Mazda 3. The i-stop symbol on the instrument panel lights up when the car is on the move and goes off when the car stops. When the engine restarts on its own, the i-stop symbol goes off for a few seconds and lights up again. Should the symbol be off when car is on the move? My car mechanic says it could be because the i-stop system battery voltage is insufficient, but I am not sure what this means.

In newer Mazda cars, the yellow i-stop warning indicates that the stop-start function is deactivated. This light will come on when the function is manually switched off, using a button that is marked "i-stop OFF". It should come on by default whenever the engine is restarted manually.

A constantly lit warning that comes on by itself indicates a fault in the start-stop system. The most common cause is low battery charge. Replacing the car battery will reset the function to its normal state.

Before that, you should also have the alternator, which charges the battery, checked to ensure it is working properly. Otherwise, the new battery will weaken in a short time and the fault will recur.

Unlike most stop-start systems, Mazda's i-stop does not rely on the starter motor to restart the engine. Instead, when the engine shuts down at a traffic junction to conserve fuel, it does so when one piston is in its compression phase. To restart, fuel is injected directly into the specific combustion chamber while the ignition module fires the spark plug.

Even though the starter motor is not required, a healthy battery is necessary so that during i-stop shutdown, auxiliaries such as the air-conditioner blower, radio or headlights will stay switched on.

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