Get a UNIVERSAL 3-WIRE O2 sensor!!! It should cost $40-$60 at a local auto parts store. DO NOT use a single-wire sensor for your 1990 car!

Several people have adapted OLDER 240s to use the single-wire unit, but "newer" 240s have engine computers that are DESIGNED to use 3-WIRE SENSORS!

As you know, the 3-wire unit has a heating element that allows it to QUICKLY reach its operating temperature (600+ degrees???). If you install a single-wire O2 sensor on a "newer" 240 that uses a heating element, here is what happens: the engine computer checks the O2 sensor after several seconds; the single-wire sensor has not heated up in time, so the computer thinks it is faulty; an error code is set, and the "Check Engine" light appears. If you reset the error code and start the car, this will happen again and again.

This occurred to my 1991 brick several weeks ago. I thought I was saving money by installing an inexpensive single-wire unit, but I did not know how the heating element was tied in with the "Check Engine" light. I posted a message, and guys on the Brickboard immediately told me the cause. A few days later, I replaced it with a 3-wire sensor.

BOSCH Universal 3-Wire O2 Sensor - Part #13077 - $47.99 at AutoZone

[[ southern fried volvo - '91 240 123k mi ]]