The CEL that won't die

[jcslocum]

We had constant CEL codes on out Mini Cooper. I chased this by changing O2 sensors and it did not resolve, until I found that the mini originally came with NTK o2 sensors and did not like the new Bosch sensors. Once the NTK were installed, the codes have never come back.

Just my .002 to your problem.

[Topless]

Look at the wiring from sensors to DME. I suspect a mouse may have chewed his way through a bulkhead pass thru and you have intermittent contact with ground.