Engine start / stop button
Starts and switches off the engine on a car with a keyless or push-button ignition.
What pressing it does
With the brake pressed (and the clutch, on a manual), a press starts the engine; with the car stopped, a press switches it off. Without the pedals, presses step through the ignition positions: on Hyundai's Tucson OFF → ACC (accessories, steering unlocked) → ON (warning lights can be checked) — it warns not to leave it in ON with the engine off, which drains the battery.
Check your car's manual: makes and models differ in what a button does, which positions a switch has and whether it works with the engine off, and your owner's manual is the authority for your car.
- What it looks like
- A circular arrow, or the words START and STOP
- Also labelled
- ENGINE START STOP; Push-button start; Power button
- Standard
- UN R121 and FMVSS 101
What to check in your car's manual
How to stop the engine in an emergency on your car, and which pedal must be pressed to start.
Where makes differ
This is not the auto stop-start button (an A inside a circular arrow), which only stops the engine automatically at standstill. Hyundai's Tucson stops the engine in an emergency when you hold the button for more than two seconds or press it three times within three seconds, and warns never to press it while moving except in an emergency, because steering and brake assistance are lost.
Where the regulations list it
| Rule | Row | Function | Must be lit with the headlamps |
|---|---|---|---|
| UN R121 | Table, item 35 “Engine start” | Control | No |
| UN R121 | Table, item 36 “Engine stop” | Control | Yes |
| FMVSS 101 | Table 2, “Engine Start Control”: the words “Engine Start” | Control | — |
| FMVSS 101 | Table 1, “Engine stop”: the words “Engine Stop” | Control | Yes |
UN Regulation No. 121 (01 series), location and identification of hand controls, tell-tales and indicators: Cars (M) and light goods vehicles (N1) approved under the UN 1958 Agreement, which includes the EU, UK and Japan. Paragraph 5.2.1: where fitted, a control listed in the table is identified by the symbol in its column 2; note 2 says the symbols are substantially identical to those of ISO 2575:2004. US Federal Motor Vehicle Safety Standard No. 101, Controls and displays (49 CFR 571.101): Cars, multipurpose passenger vehicles, trucks and buses sold in the US. S5.2.1: a control listed in Table 1 or Table 2 is identified by the symbol in column 2 or the word or abbreviation in column 3. S5.3.1(a): a control marked 'Yes' for illumination must have its identification lit whenever the headlamps are on, except on the floor, console, steering wheel, steering column or windshield header.
Good to know
- UN R121 note 19 allows 'START' and/or 'STOP' in words instead of the symbols; FMVSS 101 uses the words 'Engine Start' and 'Engine Stop' where engine control is separate from the key lock.
Related dashboard pages
Other buttons under “Horn, triangle”
Sources
The symbol is cited to the regulation rows above; what pressing it does is taken from the owner's manual below. Each document was read on the date shown.
- UN R121: UN Regulation No. 121 (01 series) as published in the Official Journal of the EU, L 5, 8 January 2016, pp. 16-19: table 'Symbols, their illumination and colours' checked 2026-09-25
- FMVSS 101: govinfo: 49 CFR 571.101 in the Code of Federal Regulations, 1 October 2025 edition, Table 1 (pp. 329-332) and Table 2 (p. 334) as printed checked 2026-09-25
- Hyundai 2025 Tucson (general market, English web manual): Engine Start/Stop button — OFF, ACC, ON and START positions; emergency stop by holding over two seconds or three presses in three seconds; battery warning. checked 2026-09-25
Written in our own words; the manuals cover their own models only.