Check engine light

If it works, wonderful. But be aware, all O2 sensors compare the oxygen in the exhaust stream to the oxygen in the atmosphere. Most sensors get their air sample through an opening between the four wires where they enter the sensor. It is possible to render them ineffective by getting carried away with rustproofing.

A few sensors draw their external air sample through one of the wires, between the wire and its insulation. Those wires can not be spliced; you'll have to replace the entire sensor.

Sorry that I can't remember which brands or models of car used those sensors, but just in case you still have trouble after the repair, consider having it tested by a professional. Their equipment will show the reading switching from rich to lean many times per second if it's working correctly. If it doesn't switch normally, the engine computer will detect that and set one or more appropriate diagnostic codes in memory, but there is a series of conditions that must be met before it will rely on any self-test results. If all the conditions are met, and the computer sees a problem, a typical fault code might be "O2 not switching from rich to lean". There are other fault codes that will not cause the Check Engine light to turn on but if set in memory, they can prevent some self tests from running.

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