mechanic says po302,304,305 300 all connected.
po code 174- o2 sensor too rich...what's up on 1998 Volvo S70
Do you have all those codes? The 300's are for cylinder misfires. Having a misfire too long or too bad will also cause damage to your catalytic converter. There are oxygen sensors before and after the catalytic converter to more accurately monitor your air and fuel mixture. We are diagnostic specialist and we also specialize in Volvo repair. Bring it for diagnostics and an accurate answer to your vehicles faults.