New Error Codes

[VT_Q45]

My '99 Q45 had a bum knock sensor, so I got that replaced about a month ago. A week or two later the service engine light came on again, but this time the OBD says it is my O2 sensor (error codes P0138 and P0139).

I have 3 questions:

-Could the mechanic working on the knock sensor have done anything to cause the O2 sensor to fail? Or is this bad luck?-How urgent is the fix to the O2 sensor?-How much should the repair cost?

Thanks for any help!

[Q45tech]

We call this the ever since syndrome owners trying to find any excuse to blame technicans for any unrelated future failure.Ever since you changed the oil, the ac and window doesn't work and the tag light and shocks are leaking and Britney Speers forgot how to sing. It all your fault.

Anything is possible but probably just normal failure.

P0138 Rear O2S, Bank 1 Maximum Voltage Monitoring P0139 Rear O2S, Bank 1 Response Monitoring

[VT_Q45]

Regardless of how the sensor failed, how urgent of a problem is it? And how much is the repair? Thanks!

[Q45tech]

Every car made since 1996 has had a front and rear [after cat] O2 sensors.

Most V8/V6 have 2 of each, a common wear and tear item replaced after warranty expires say every 80,000 miles like shocks.

[bullittandy]

All four O2's are about $300 in parts if I remember correctly and maybe $200 in labor. Not an URGENT repair but don't put it off for more than a few thousand miles.

[bullittandy]

[QUOTE=Britney Speers forgot how to sing. It all your fault.[/QUOTE]

Ohmigod, like, its SpeArs.

Say tech, what'd ya think of her performance on the VMA's?