Car Engine Datalogger
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Copyright 2009 Jonathan Oxer
Copyright 2009 Hugh Blemings

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| This project is featured in the book "Practical Arduino" by         |
| Jonathan Oxer and Hugh Blemings (Apress, 2009). More information    |
| about the book and this project is available at:                    |
|                                                                     |
| www.practicalarduino.com/projects/car-engine-datalogger             |
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Ever wondered what goes on under the hood of your car? Wish you could
peek inside the engine management system and read values from it?
Annoyed that your dashboard shows a cryptic "Check Engine" light (CEL)
but no explanation about what the problem might be?

All cars and light trucks sold in the US since 1996 have been required
by law to provide a standard interface called "OBD-II" (On-Board
diagnostics version 2) that provides access to a variety of operational
data about the vehicle. Europe followed in 2001 for petrol vehicles and
2003/4 for diesels with the "EOBD" (European OBD) standard which is
basically just OBD-II with a different label.

Because car manufacturers try to standardise their production lines as
much as possible OBD-II vehicles also found their way into many markets
outside the US as early as 1996. Japanese car manufacturers, in
particular, deployed OBD-II in all markets very rapidly even when not
legally required to do so. The result is that when you take your car to
an auto mechanic the first thing they usually do is plug in a laptop
using a USB to OBD-II adaptor, then run some software that interrogates
the engine management system to retrieve stored information such as
faults that have been logged automatically since the last service.

But you don't need a full laptop computer to get access to the data.
With this project we modify a commonly-available OBD-II adaptor so you
can link an Arduino to your car and log data in real time as you drive
around. By reading and storing OBD data you can create a "black box"
flight recorder for your car - use it to generate graphs of vehicle
performance, or record a complete snapshot of all engine management
parameters at the moment a fault occurs, or even as evidence that you
weren't speeding if you're involved in an accident!