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Is it possible to start an automatic car whilst in drive? If it does start in drive, is this considered dangerous?

user7787
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2 Answers2

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Automatic transmission have what is called a neutral safety switch (NSS). This ensures the engine should not start while the transmission is in some other position besides Park or Neutral. It should not start, so if it is, it means there is a fault with the NSS. Most occurrences I've heard of is where if the NSS is bad, it will not allow the engine so start in any selector position, though I don't see where your suggestion is out of the realm of possibility. Having the transmission engaged while starting could lead to loss of control of the vehicle (surprise at the vehicle moving when it shouldn't), so yes, it is considered dangerous.

Pᴀᴜʟsᴛᴇʀ2
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Most automatic transmissions are equipped with a NSS (neutral safety switch). All that does is making an open circuit to the starter motor relay so you can't start. However, you can bypass this by jumping the starter motor relay with a wire and supplying a 12v positive to engage this relay. Make sure you fully depress the brake pedal while doing this and your engine has reached the regular running temperature. I don't foresee any transmission damage etc. But do this at your own risk. Late model vehicles may already equipped with an auto start stop feature which stop your engine at traffic lights etc. These vehicles does not shift to neutral or parking when restarting..they restart while the gear selector is at D and after you lift feet off the brake pedal. Keep in mind that the module controlling this feature is a chip programmed for this specific function and collect more data like engine temp, speed, incline, ave. idling rpm etc. prior to making decisions and may even be more advanced than I can explain here. Hope this explains why you cannot start on D (because of possibility of vehicular damage due to moving - (although older manual transmission vehicles allow you to start in any gear without depressing the clutch pedal)). Be safe until next time. LR - Brampton, ON

Leonel
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