I suspect that your cord is defective.  Mine works fine in ETTL mode.

I will go to the store today for a comparison. Will keep you guys posted. Thanks.

Well the mystery has been solved - it was indeed a bad cord.

I returned to the store, tried another seemingly identical cord, and this time E-TTL worked. The store owners were as mystified as I was as to why a brand-new cord didn't work (my first one).

In any case, all is currently well. My 10d, 550EX, and OCSC2 are all now working in harmony.

Cheers to all who read this thread and responded.

RS - Comments on other boards suggest that contacts sometimes need to be cleaned to ensure proper working ; that might be the case with your cable if it is 5 years old.

I just picked up the Canon Off Camera Shoe Cord 2 to use with my 10d and 550EX. The problem is, it doesn't seem to work in ETTL mode.

My 550EX works in ETTL mode when directly attached to my 10d, and my Ellan II. However, once the cord is introduced into the mix I go into TTL mode (on both cameras)

Zoom ceases to work, exposures are WAY off.

Has anyone had this issue before? I have searched all the usual places on the net, and have had no luck tracking down a similar problem.

Is one of the 4+1 pins specifically involved in the 'E' of 'E-TTL' ?

I agree with englishm - try a new cord. Perhaps go to a local camera store, and see if they've got one they'll let you compare against?? Since it's doing it with both cameras, and the flash works fine otherwise, this would be the first logical troubleshooting step. AFAIK, the flash and camera shouldn't notice any difference with the cord in between them....

    Somewhere out on photo.net I recall seeing a pointer to the pin usage for E-TTL vs. normal TTL metering on these cameras, but I don't seem to have it handy anymore. A search there might turn up some help...

    Dave

I have the same problem. Bought the cable about 5 years ago.