I would suggest following the wire from the sensor and see where it goes. There were a multitude of ways people created lambda control. Before you try and understand lambda control you might as well figure out if and how they do it.

One way that was done was to take the coolant temp sensor and cut the wire. They would feed both ends into a new box that would read the O2 sensor and change the effective resistance of the temp sensor to alter mixture. It was a terrible method and never stayed in adjustment for any length of time. Some cars would actually just need to have the O2 sensor hooked to the original computer and some people changed the controllers and added the O2 sensor. You should determine what you have and go from there.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician