Actually it's C1, C2 and CU (not C3), and these can also be further divided into Exy errors, but no drive I know of is capable of reporting the Eyx errors individually - at least not with commonly available scanning software.
C1 = E11 + E21 + E31 (or maybe C1 = E11 + E21 for some scanning drives?)
C2 = E22 (or maybe C2 = E12 + E22 for some scanning drives?)
CU = E32
At least for Plextor drives the above Cx = Eyx... equations hold true.
C1 very roughly translates to PIE for DVD media and CU very roughly translates to POF. C2 doesn't realy translate very well to PIF since a good CD should have zero CU as well as zero C2.