You can set the AMM without a CO meter, if you have a lambda (oxygen) sensor. The lambda voltage at the test connector (I forget where) is from 0 to 12v, but the lambda voltage from the lambda itself is 0 to 1v and can be measured best with a cheap "narrowband air fuel ratio" gauge. Often voltmeters (even analog ones) aren't fast enough to catch the quick fluctuations in voltage, which is why I recommend the gauge, which works with LEDs (like the tacho on a trabi ).

Of course, the point is moot if your LH 2.2 is non-lambda.