Check engine light came on in 2000 E320, 41,600 miles. Went to Auto Zone to obtain OBD II tool. Pulled up one code only, PO173-fuel trim management, bank 2.

AZ employee looked at his guide and said it might be the O2 sensor. Bank 2 would be the passenger side? Is there more than a single O2 sensor for bank 2?

Does DTC PO173 identify the O2 sensor as bad? In CA, is the O2 sensor covered under the CA emissions control systems warranty?

Thanks for any info.