DIY_EFI Digest V5 #150

[Scott Croughwell]

> So, what do those US$90 boxes do? Anyone scoped them?

It just makes the voltage jump around from 0v to 0.5v.  The OBD-II ECU's
play "tricks" to check the oxygen sensors, such as drop a lot of fuel into
the cylinders (when cruising or idling) to make sure the sensors respond.
I'm sure the $90 box just outputs a sine wave... steady or random, I'm not
sure.  Also, when you shut off the ignition, the heaters to all the oxygen
sensors are turned on x minutes after shutdown (depending on water temp) to
both test and clean.

Scott

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