96 740 OBD Codes 10 & 15 after O2 changed

[jimrad]

1996 740 il with 138,000.

Recently, my check engine light went on. After using both my generic OBD II code reader, and Peake research code reader, it became apparent that the precat O2 sensor on bank 2 was not working properly. (which has been in the car for at least 5-6 years). Based upon an article on e38.org, I purchased 2 OEM Bosch pre-cat sensors & installed them.

Shortly there after the check engine light came on again. The BMW codes then read 10 & 15. I assumed that maybe I had purchased defective pre-cat Bosch O2 sensors, and have since replaced them now 3 times. The check engine light still comes on with BMW codes 10 & 15.

The original O2 sensors removed from the car had a Bosch number of 0 258 003 802. I have replaced them with what the dealer had in their computer as the appropriate part which is Bosch number 0 258 003 559.

After replacing the pre-cat sensors now 3 times I need help. Any thoughts?

JTR