I have an 89 240 wagon. Took it to the shop and they repalced the oxygen sensor. After that, the car ran fine for a day and then the check engine light came on again.
The shop replaced the oxygen sensor , a 4 wire, with a 2 wire. Could this be my problem?
I am now getting code 231 "fuel system compensating for rich or lean at cruise." My gas mileage has not improved.
Any ideas. I would rather change a few sensors than take it back to the shop.
thank-you

 

Sounds like a diferent O2 sensor to me....I would get a 4wire in and then you should have no more codes.

Wait for others to reply........

 

Your car should have a 3 wire from the factory.