GE OEC 9900A/D channel 15 failure upon boot

Hi,

I have a 9900 that stalls around arrow 11 and then comes up with an Error on the Doghouse   " A/D Channel 15 failure".   Looking at the manual it says   Channel 15 is a signal on GIB " D/A test".  I've replaced the GIB and I still have the problem.  Anyone seen this before?

Thanks

Donna