Check Engine Light

The engine light on my 92 525i comes on when I decent from altitude >6000', but goes off after a short while when at <1000'.
When I checked the codes it returned an oxygen sensor fault, but I changed that a few months ago.
Is it possible that extended running at low speed and at altitude when descending can cause a fault? The cars seemed to run fine otherwise, but
I'd be interested to know what's causing it.

Any ideas?

Thanks

reboot the computer and check the code again when it happens, could be a fluke.