Volvo: How to turn off check engine light on 1990 240, volvo 240 dl, oxygen sensor

Question
I have a 1990 Volvo 240 DL.  The previous owner had it in Bahrain for a couple of years, had the catalytic converter removed and returned, and the exhaust system is now welded in a way that makes access to the oxygen sensor very difficult. My mechanic has determined that the Check Engine light is coming on because of the oxygen sensor, but he can't get to it, and it doesn't affect the running of the vehicle.  How can I simply turn off the Check Engine light?

Thanks!

Jeff Stark
Falls Church, VA

Answer
Because the light coming on is connected to a failing oxygen sensor, which triggers the ECU computer, the only way to turn the light off would be to physically disconnect the wire from the back of your instrument cluster, or manually remove the lightbulb from that display.  I hesitate to recommend this for several reasons.  First, with a bad oxygen sensor, your car will run worse, and you'll mostly likely see a drop in fuel economy, because your car will run richer due to lack of information about the fuel mixture normally coming from the oxygen sensor.  Second, you won't be able to pass smog the next time you have to take it in, even if the light is turned off, because without the sensor working, your car is putting out way to many hydrocarbons to pass.  So in the long run, you're going to have to mess with getting the oxygen sensor out, unless you know you can pass smog, and you don't mind reduced mileage and performance.