My new to me 99 S70 had the check engine light right after I bought it. I took it to the dealer. At 1st they thought it was the catalytic converter. Since that's under warranty, they took their time and decided instead to replace the Mass Airflow Sensor (302 of my $). Thereceipt says "The car's mass airflow sensor faulty and causing o2 sensors to read out of range."
Right after I picked up my car, the CEL came back on. Now the dealership is saying "THE CHECK ENGINE LIGHT IS ON AS A RESULT OF A FAILED OXYGEN SENSOR FRONT. FAIL CODE ECM4801 THREE WAY CAT. ALL TEST SHOW THAT FRONT OXYGEN SENSOR IS NOT OPERATING CORRECTLY, IT IS NOT SHOWING THAT IT IS READING ANY MEASUREMENTS COST 445.00"
The service writer says that the O2 sensor was compensating for the mass airflow sensor, but now it's out of that range and "gave up (not reading any voltage)" As far as I know, O2 sensors don't exhibit learned behavior...am I being hosed?
I'd appreciate any alternate theories.
Thanks