My check engine light went on. I read the code and got only a Code 3 (Lambda control inoperative). The car runs fine. Where do I start looking for the problem?

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95 E320 Cabriolet, 169K

Erase it and see if it comes back, if so, replace the oxygen sensor.

See what it is coupled up with at pin *8

Arthur, how do I perform this procedure?

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95 E320 Cabriolet, 169K

with an LED code tester...you can build your own:

http://members.aol.com/ajdalton7/ledtool.jpg
also check out this thread: E320 16 PIN DTC Charts inc. pin 8, pin 14

or buy one from me...see my ebay link

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE

Hey
Do I get Royalties ???????????????????????????????

Just make the tool and then you can get the codes from the other modules .
R Shack parts .. $5 will do it.
Getting the codes is the same as the built in sw/led you used for the diagnostics module. Interpretation is the key.. post what you find.