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A lot of people want the check engine light to go off.

I am doing some research for school and I want it to come on. Does anyone know some simple problems or faults I can create with a vehicle in order to make the check engine light come on?

These would be faults that the car can run with (not necessarily drive with) without causing permanent damage, hopefully.

I am trying to develop software for a school project that can track Error codes going on and off over time.

I understand that any advice you give is for educational purposes and don't hold anyone here accountable if something goes catastrophically wrong.

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    Welcome to the site, and great question! Hope you get a wide range of answers on this one.
    – Zaid
    Commented Mar 3, 2016 at 20:12
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    Your getting some good action on this question. Thanks for contributing to the site with it. Cheers!
    – DucatiKiller
    Commented Mar 3, 2016 at 20:59

5 Answers 5

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The CEL trigger implementation will vary across vehicles, but here are a few for you to try out. They should not have any negative effect in the long-term on the vehicle:

P010x - unplug MAF sensor

P030x - unplug a spark plug wire/coil (unplugging the corresponding injector is recommended)

P0420/P0430 - unplug the O2 sensor after the catalytic converter

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  • Unplugging the cam sensor will also allow it to run. The crank position sensor will not however, and it is located neae the bottom of the engine, only do so if you do not want the engine to turn over at all.
    – Tobin S
    Commented Mar 25, 2016 at 14:06
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Start unplugging stuff. The engine will normally run with a lot of the sensors unplugged, but the check engine light will come on quickly.

Some easy to reach ones: Mass Air Flow (MAF), Oxygen sensors, sometimes the throttle position indicator (on the throttle body).

If you can unplug the power to the secondary air injection pump, it will cause a fun light that will only come on after driving it for a few times.

Unplugging a fuel injector should lead to a flashing check engine light.

Most (if not all) of what I mentioned should make the light go back off once corrected. You might have to complete a few drive cycles for some of them to "reset".

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@JPhi1618 answer is good.

I would just add a few more,

  1. You can unplug the EGR Valve electrical connector, no harm to engine.
  2. Pull out a coil pack or coil wire.
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  • If you're going to unplug a coil instead unplug the injector that way you're not dumping fuel into the converter.
    – Ben
    Commented Mar 3, 2016 at 20:51
  • The unburnt fuel will burn in the cats and more over this is only for a test. This is just one of the possibility to get the check engine light on.
    – kasey
    Commented Mar 3, 2016 at 20:57
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To add to the list, run the engine without the fuel filler cap on.

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  • This will (for a Mk1 Ford Focus) cause the engine management light to come on. Not sure if that's the same issue in all vehicles. Source: it happened to my mum
    – gabe3886
    Commented Mar 4, 2016 at 13:27
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Hi like on opel astra when ur remove fuse numa 20 in fuse box engine light will come on radiator fan won't come on nd it will only run in low gear thts only on the automatic opel astras

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  • This is very specific and a little unclear. Perhaps you could edit the answer to be more general and improve the language/formatting?
    – JPhi1618
    Commented Mar 3, 2016 at 21:32
  • Yes, please do. You can also combine your posts. If you think of more things to add you can just edit your original post and add it in.
    – DucatiKiller
    Commented Mar 3, 2016 at 22:26

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