Ok is a 1992 volvo 240 it has the check engine light on. No misfiring, no heavy start on morning starts very fast but it has the CEL on it my sister car she said that since the light got on it consuming a lot more gas than before need advise..

Codes




2-1-2
Oxygen sensor signal(front sensor on 94 and later models).



2-3-1
Lambdfa adjustment.

 

Sounds like the O2 sensor. But...

First check for vacuum leaks.

If you have a voltmeter, you can check the voltage of the sensor.

Make sure the engine is up to operating temperature, pull back the connector boot, on the green wire, and leave the sensor connected. Connect the voltmeter and the reading at idle should sweep between .2-.8 volts.

Hope that helps.

B