1991 Other Mercedes Benz Models Oxygen Sensor / Check Engine

The o2 sensor(s) are located after each exhaust manifold before the catalytic converter, also there may be one or two after the catalytic converter.

On a warm hot day start the car up and slowly spray mist of water on various parts of the car under the hood, one bit at a time, if there is a short you will see it sparking or the car will start to die down, post back the results.