[Mk2] [NA] Engine check light not working

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Hi
My friends engine check light is not working, I have read somewhere
you can check for codes using a battery and bulb, anyone know
how how to do it, thanks in advance.
Cheers

[Quigonjay]

http://www.ayrpark.plus.com/errorcodes.html

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Thanks for reply, but what I was really after was a way
of doing it with a test lamp and battery, I have seen it
somewhere, but can`t find it again.