Don't know where you live, but in the US, all cars of that era and
forward have a universal system which has a std connector and can be
read out with any of the aftermarket code readers. One company is
Actron. These readers will read and reset the general codes common
to all cars, ie cylinder X missfire, air/fuel mixture too rich, fuel
evap system leak, , etc. There is manufacturer/model specific
additional info that takes a more specialized reader. An example
would be some cars have climate control system info that a more
specific reader can access. But for DIY the Actron type works very
To find out what a particular code means, you can check the websites
of the code reader manufacturers, like Actron. I've also gotten a
lot of info by just typing in the car/code with a google search of
both the web and newsgroups. Search would be for "E420 code PXXXX",
There is online source... the basic gist of it is by your battery in that
rectangle diagnostic port... there is a button. With ignition on, I think
you press the button for 2 seconds and it will start blinking out codes.
Do a seach online... W124 obd.
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