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The exact name, symbol, indicator color, restart behavior, and reset procedure vary by make, model, year, engine, transmission, and trim. If the button is labeled A OFF, ISG OFF, Auto Stop Off, or something similar, your owner’s manual is the final authority.
Quick answer
The capital A inside a circular or semicircular arrow most commonly identifies automatic engine stop/start. The system stops the internal-combustion engine while the vehicle is stationary to reduce idling, then restarts it automatically when driving, climate-control, battery, or safety requirements call for it.
It is normal for the engine to stop at a light while the car’s electrical systems remain on. It is also normal for the engine not to stop every time. If you see a flashing symbol, a persistent amber warning, a malfunction message, or the engine fails to restart normally, follow the vehicle’s instructions and have it inspected.
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How to identify the “A in a circle” symbol
The feature is highly likely to be automatic stop/start when you see one or more of these clues:
- An A surrounded by a circular arrow or curved arrow
- A button labeled
A OFF,AUTO STOP OFF,ISG OFF,i-stop, or a similar term - The button is near the gear selector, center console, or driver-information controls
- The engine sometimes shuts off when you are stopped with the brake applied
- A matching A-shaped symbol appears in the instrument cluster when the system is active, available, disabled, or temporarily unavailable
The letter generally suggests “automatic” operation, while the circular arrow suggests a repeated stop-and-restart cycle. That is a useful visual clue, not a guarantee that every similar-looking symbol works identically. Road-vehicle symbols are covered by standards such as SAE J2402, but manufacturers still use different labels, indicator logic, and operating rules.
Also check whether you are looking at a physical button or an instrument-cluster status light. A physical A OFF button generally gives you control over the feature. A green A symbol in the cluster may simply tell you that the engine is currently stopped. Those indicators are not necessarily interchangeable.
Look at the button’s location, not just the letter
A symbol that only resembles an A or a circular arrow can control something else. Two common lookalikes are:
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- Auto Hold: A brake-holding function that keeps the vehicle stationary after you release the brake pedal. It does not shut off the engine by itself.
- Air recirculation: A climate-control button usually showing a car with a curved arrow inside it. It recirculates cabin air and is unrelated to engine stop/start. Hyundai’s climate-control manual shows this as a separate function.
If the icon is beside the climate controls rather than near the shifter or driver controls, check the label and owner’s manual before assuming it is stop/start.
What happens when automatic stop/start activates?
For a typical automatic-transmission vehicle, the sequence looks like this:
- You drive normally.
- You come to a complete or near-complete stop.
- You keep the transmission in the manufacturer-specified position, commonly Drive, and apply the brake.
- The vehicle checks conditions such as engine temperature, battery charge, climate demand, steering angle, vehicle position, and door or hood status.
- If all requirements are satisfied, the engine stops while the vehicle remains switched on.
- The engine restarts when you release the brake, press the accelerator, change gear, or when the vehicle decides the engine is needed for climate control, battery charging, braking support, or another safety or drivability requirement.
Chevrolet describes the engine stopping at a complete stop and restarting when the brake is released. Honda documents similar behavior for its Auto Idle Stop system, although the exact trigger depends on the vehicle. You can compare the manufacturer examples in the Chevrolet Stop/Start explanation and the 2020 Honda Odyssey guide.
Does the car turn completely off?
No. The system normally stops the engine, not the entire vehicle. The ignition and electrical systems remain in an operating state, so the audio system, displays, climate controls, lighting, and safety systems may continue operating according to the vehicle’s design.
Do not treat an automatic engine stop as permission to leave the vehicle. Before exiting, select Park and switch the vehicle off using the normal procedure in the owner’s manual. Some vehicles can restart the engine automatically while stopped; Toyota specifically warns owners about this possibility in its Stop & Start instructions.
How to turn the feature off
Most vehicles with a dedicated switch use this general procedure:
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- Locate the button marked with the A-and-arrow symbol, often labeled
A OFForISG OFF. - Press it once. If you are in traffic, do this only when it is safe and practical.
- Check the instrument cluster or center display for a message or indicator confirming that Stop/Start has been disabled.
- Press the button again if your vehicle allows you to re-enable the system manually.
Do not assume that an illuminated button always means “on” or that an unlit button always means “off.” Indicator conventions differ:
- Chevrolet says its Stop/Start switch LED is not illuminated when the system is off.
- Honda documents an amber Auto Idle Stop indicator when the system is off.
- Volkswagen says its button illuminates when the system is deactivated.
Read the accompanying message or the manual for your exact vehicle. The Chevrolet documentation, Honda guide, and 2026 Volkswagen Taos quick-start guide demonstrate why the same light cannot be interpreted universally.
Will it turn back on the next time I start the car?
Often, yes. Many systems are designed to re-enable automatically at the next ignition cycle. Chevrolet says Stop/Start is enabled each time the vehicle is started. Honda says Auto Idle Stop turns on again every time the engine is started, even if it was turned off during the previous trip. Volkswagen’s 2026 Taos guide likewise says the system is automatically activated whenever the ignition is switched on.
That is not a rule for every vehicle. Some models, drive modes, or markets may behave differently. A dedicated button usually provides a temporary, one-drive-cycle disable rather than a permanent setting. Do not use aftermarket wiring changes, sensor tricks, or software modifications as a normal way to defeat the system; they can create diagnostic, emissions, warranty, or safety problems.
Why does the engine sometimes not stop?
A stop/start system is allowed to refuse an automatic stop whenever stopping the engine could affect comfort, battery condition, drivability, or safety. A message such as Stop/Start unavailable does not automatically mean the system is broken.
| Possible reason | Why the engine may keep running |
|---|---|
| Cold engine or transmission | The vehicle may need the engine running until operating temperature is reached. |
| Low 12-volt battery charge | The system may preserve battery power or run the engine to recharge the battery. |
| High electrical demand | Defrosters, heated equipment, lighting, or other electrical loads can inhibit an engine stop. |
| Heating or air-conditioning demand | The engine may need to run to maintain the requested cabin temperature or windshield visibility. |
| Defrost or defogging selected | Maintaining a clear windshield can take priority over fuel-saving stops. |
| Steering wheel turned | Some systems avoid stopping during a steering maneuver or when additional engine assistance may be needed. |
| Vehicle on a slope | The system may prevent a stop on a significant incline or decline, depending on the model. |
| Door, hood, or seat-belt status | The system may require specific driver, hood, and door conditions before stopping or restarting. |
| Drive mode or transmission condition | A selected drive mode, gear, clutch position, or transmission temperature may inhibit the feature. |
| Minimum-speed or timing requirement | Some vehicles require you to drive above a certain speed or wait a specified period after the previous stop. |
| Accelerator input or creeping movement | The engine may remain running when you are maneuvering, creeping, or asking for immediate power. |
| Maximum stop duration | The engine can restart automatically after it has been stopped for the system’s permitted time. |
These safeguards are documented in different forms by Chevrolet, Kia, Hyundai, and Honda. The exact list for your car may be shorter or longer.
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Why does the engine restart while I am still stopped?
An automatic restart before you release the brake can be completely normal. The vehicle may restart to:
- Maintain heating, air conditioning, or windshield defogging
- Restore 12-volt battery charge
- Maintain brake-vacuum pressure or other braking support
- Support engine or transmission operation
- Respond to steering, vehicle-position, or safety requirements
- Prevent the automatic stop from lasting longer than the permitted duration
The driver may notice a vibration, starter sound, or change in engine noise when this happens. A restart by itself is not evidence of a malfunction. A persistent warning, rough restart, or failure to restart normally is a different matter.
Does stop/start work differently with a manual transmission?
Yes. The commonly repeated explanation—“the engine restarts when you release the brake”—primarily describes many automatic-transmission vehicles.
With a manual transmission, the system may stop the engine after you slow or stop, select neutral, and release the clutch, if the model’s conditions are met. It may restart when you press the clutch or select a gear. Kia provides separate operating rules for automatic and manual transmissions in its ISG owner information.
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Because clutch position, gear selection, hill-start assistance, and driver input affect the sequence, use the manual’s instructions rather than applying the automatic-transmission procedure to a manual car.
Is automatic stop/start bad for the engine, starter, or battery?
Vehicles equipped with the feature are designed for substantially more start-and-stop events than vehicles with a conventional idle cycle. Manufacturers use starting-system and battery specifications intended to handle that additional cycling. Chevrolet says its engine and starting system are designed for increased Stop/Start activity, while Ford describes using a heavy-duty starter and battery for vehicles with Auto Start-Stop. The Department of Energy also explains that non-hybrid stop/start systems use engine architecture intended to reduce premature wear from frequent restarting.
That does not mean the components experience no wear or that every replacement battery will work. The 12-volt battery still ages, the starter and related components can eventually require service, and a weak or incorrectly specified battery can prevent Stop/Start from operating. Honda specifically warns that the specified 12-volt battery should be used because an incorrect battery can shorten battery life and prevent Auto Idle Stop from working.
In practical terms:
- Do not disable the feature solely because you assume normal operation is damaging the engine.
- Do not replace the battery solely because Stop/Start is temporarily unavailable.
- When a battery is needed, use the type and specification required for the vehicle.
- Have persistent battery, charging-system, or Stop/Start warnings diagnosed rather than guessing at the part.
Relevant information is available from Chevrolet, Ford, Honda, and the U.S. Department of Energy.
Does it really save fuel?
Yes, it can, but the benefit depends heavily on how and where you drive. The U.S. Environmental Protection Agency says start-stop systems can improve fuel economy by approximately 4% to 5%, with the greatest benefit in stop-and-go city driving where the engine would otherwise spend considerable time idling.
That is a general estimate, not a guarantee for every vehicle or driver. Actual results vary with traffic, stop duration, climate-control use, outside temperature, engine type, and how often the system is permitted to operate. A long red light provides more opportunity for fuel savings than a series of very short rolling stops.
Automatic stop/start is also not the same thing as a hybrid powertrain. In a typical non-hybrid stop/start vehicle, the gasoline or diesel engine shuts off at a stop, but the vehicle is not propelled by an electric motor. The Department of Energy’s comparison of stop/start and hybrids explains the distinction.
What do the different A symbols and colors mean?
There is no universal color dictionary that applies to every make and model. The same amber or illuminated button can mean different things on different vehicles. Treat the following as common examples, not a substitute for the manual.
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|---|---|---|
| A inside a circular arrow | Stop/start system status or control | Check whether it is a button, a cluster indicator, or a message icon. |
A OFF, ISG OFF, or crossed-out A |
The system may be manually disabled or temporarily unavailable | Read the message and check whether it returns after the next ignition cycle. |
| Green A or “Auto Stop” indicator | The engine is currently stopped or the system is actively operating | Keep the vehicle secured and remain ready for an automatic restart. |
| White or gray A indicator | The system may be available but not currently stopping the engine | Normal operating conditions may not yet be satisfied. |
| Amber or yellow A indicator | The system may be switched off, suspended, or reporting a problem | Use the accompanying wording and owner’s manual to distinguish these cases. |
| Flashing symbol or A with an exclamation mark | Possible system fault | If it persists or appears with other warnings, arrange an inspection. |
For example, Honda uses a green Auto Idle Stop indicator for an active engine stop and documents an amber indicator when the function is off. Hyundai uses green and white states for different ISG conditions, while Toyota provides separate malfunction guidance. These differences are why a color alone is not enough to diagnose the vehicle.
What should I do if the engine does not restart?
If the engine remains stopped and does not restart in the expected way:
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- Keep the brake pedal firmly depressed and keep the vehicle secured.
- Read the instrument-cluster message. It may tell you to select a particular gear or perform a manual restart.
- If instructed, shift to Park or Neutral. Do not choose a gear that conflicts with the vehicle’s instructions.
- Use the normal ignition or engine-start procedure.
- Have the vehicle inspected if it repeatedly requires a manual restart, a warning remains, or a battery or charging warning appears.
This is a cautious general path, not a universal emergency procedure. Hyundai, for example, instructs the driver to depress the brake and restart manually in Park or Neutral if ISG has been deactivated after a hood-opening event or system problem. Your model may provide different instructions; follow its display and owner’s manual first.
If the engine will not restart using the normal procedure, treat the situation as a vehicle breakdown: keep the car secured, use hazard lights when appropriate, and get assistance rather than repeatedly experimenting with the controls in moving traffic.
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Before opening the hood, switch the vehicle off normally. An engine that is silent at a stop may be in an automatic stop state rather than fully shut down. Honda warns that opening the hood can prevent automatic restarting and require a manual restart. Hyundai likewise deactivates ISG after a hood-opening event and may require a manual restart.
This is especially important when checking fluid levels, inspecting the engine bay, or working near belts, fans, and other moving parts. Wait until the vehicle is fully switched off and follow the safety instructions in the owner’s manual.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Is it safe at intersections and in a drive-through?
Under normal operating conditions, the system is designed to operate during ordinary stops, including traffic lights and many drive-through queues. It is not autonomous driving: you still need to hold or secure the vehicle as required, watch traffic, and be ready for the engine to restart.
You may choose to disable it temporarily when repeated short movements, parking maneuvers, steep slopes, severe weather, or interrupted cabin heating and cooling make the restarts uncomfortable or distracting. That is a context and comfort decision, not a general requirement to protect the engine.
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In a poorly ventilated location, follow the vehicle’s instructions carefully. Toyota warns that an automatic restart can allow exhaust gases to accumulate if the system is not disabled. Never leave the vehicle unattended merely because the engine has stopped.
Stop/Start versus Auto Hold
| Feature | Stops the engine? | Holds the vehicle stopped? | Typical purpose |
|---|---|---|---|
| Automatic Stop/Start | Yes | Not primarily | Stops the engine during suitable stops and restarts it automatically. |
| Auto Hold | No | Yes | Maintains brake pressure after the vehicle stops so you can release the brake pedal without rolling. |
Auto Hold is normally marked with AUTO HOLD or a separate brake-related symbol. Hyundai describes it as holding the vehicle stationary and releasing the brakes when the accelerator is pressed. See the Hyundai Auto Hold instructions.
A vehicle can have both functions. Depending on the programming, Auto Hold may keep the car stopped after you release the brake while the engine remains in its automatic stop state. Hyundai and Toyota both document interactions between brake holding and stop/start. The presence of Auto Hold does not change the fact that it is a separate brake function.
Should you leave automatic stop/start on?
For most drivers, leaving it enabled is reasonable when the engine and battery are healthy, the restarts feel smooth, and the climate system remains comfortable. The feature is part of the vehicle’s original design and can provide its greatest fuel-saving benefit in city traffic.
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Temporarily turn it off when:
- The repeated restarts are uncomfortable or distracting
- You are making repeated parking or low-speed maneuvers
- Cabin cooling, heating, or windshield defrosting is being interrupted
- You are in a situation where you prefer the engine to remain running
- Your owner’s manual recommends disabling it for a particular condition
Because many vehicles automatically re-enable the system after the next start, you may need to press the button again on each trip. That temporary reset behavior is intentional on many models rather than a sign that the button failed.
What do manufacturers call the feature?
The same basic function appears under different names:
| Manufacturer example | Term used |
|---|---|
| Chevrolet | Stop/Start Technology |
| Ford | Auto Start-Stop Technology |
| Honda | Auto Idle Stop |
| Toyota | Stop & Start system |
| Hyundai | ISG, or Idle Stop and Go |
| Kia | ISG, or Idle Stop and Go |
| Volkswagen | Start-Stop System |
| Some other makes | i-stop, Start/Stop, or Auto Stop/Start |
When searching your owner’s manual, try the terms “Stop/Start,” “Auto Start-Stop,” “Auto Idle Stop,” “ISG,” “i-stop,” and “Auto Hold.” Manufacturer examples in the available documentation range from a 2020 Honda Odyssey and 2021 Toyota Highlander to 2024 Honda and Kia manuals and 2026 Hyundai and Volkswagen documentation. Those examples show the feature’s general purpose, but they are not interchangeable instructions for every model year.
When does the A symbol require service?
Make an appointment with a qualified technician when:
- The A symbol flashes repeatedly
- A yellow or amber warning remains after normal operating conditions return
- The vehicle displays a Stop/Start, ISG, or Auto Idle Stop malfunction message
- The engine repeatedly fails to restart normally
- A battery or charging-system warning appears
- Other warning lights appear at the same time
Do not replace the battery just because Stop/Start did not activate once. Battery charge is only one possible reason; cold temperatures, climate demand, steering angle, slope, timing requirements, and other normal conditions can also prevent an automatic stop. If a battery is eventually needed, the vehicle may require a specific battery type and a model-specific diagnostic or replacement procedure.
How to confirm the exact meaning in your car
- Identify the vehicle’s make, model, model year, engine, transmission, and trim.
- Check whether the symbol is on a physical button, in the instrument cluster, or on the climate-control panel.
- Read the label next to it:
A OFF,ISG,Auto Hold, or a climate-control label points to different functions. - Search the owner’s manual for Stop/Start, Auto Idle Stop, or ISG.
- Use the manual’s indicator chart to interpret the color, flashing behavior, and reset procedure.
If you need an exact identification, the make, model, year, and a clear photograph of the button and surrounding controls will usually resolve the ambiguity quickly.
Frequently Asked Questions
Can I permanently disable the A stop/start system?
Many vehicles only allow a temporary disable through the factory button, and the system re-enables at the next ignition cycle. Permanent bypasses are not recommended because wiring or software changes can create diagnostic, emissions, warranty, or safety complications. Check the owner’s manual for any factory setting or drive-mode option specific to your vehicle.
Does the A-in-a-circle symbol mean my car is a hybrid?
No. Automatic stop/start is also used on non-hybrid gasoline and diesel vehicles. It shuts the engine off while stopped but does not use an electric motor to propel the vehicle. A hybrid must be identified by its actual powertrain and manufacturer designation.
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No. On some vehicles amber means the system has been switched off or is temporarily unavailable; on others, a persistent amber or flashing symbol can indicate a fault. Use the accompanying message and the exact owner’s manual. Service is appropriate if the warning persists, flashes, or appears with battery, charging, or other warning lights.
The Bottom Line
The “A” with a circular arrow usually means automatic engine stop/start. It stops only the engine during suitable stops, then restarts it automatically; pressing the matching button generally disables the feature temporarily. Normal non-operation is often caused by battery charge, temperature, climate, steering, slope, or other safeguards. Persistent warnings or repeated failure to restart should be diagnosed, and the exact indicator meaning always depends on the vehicle’s make, model, year, and owner’s manual.
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