I just had this issue with replacing a fan in a Proliant 800. The fan worked but I continued to get the 1611 error and could not boot past it. Apparently when you order part number 122633 there are different manufacturers and amperages available. The ones I've seen are .49A,.80A, and .90A from Nidec and NMB. The original was a Nidec .80A and the replacement sent to me from a third part vendor was an NMB .90A.
After the error continued I saw the post above in this thread that mentioned getting the right amperage, so I contacted the vendor. He said he'd sold hundreds of these and never had this problem. He said he had the exact make, model, and amperage that I had in there originally, so I had him send it to me. Well, it worked.
Now I can't say for sure, but I don't think the amperage is the issue. After studying the 3 fans I noticed the Nidec fan wires were spliced to have 3 blacks, 1 red, and 1 yellow and the NMB that spun but didn't register in POST was not spliced and only had the 1 black, 1 yellow and 1 red that come from the motor. Now the pin jumper is 4 pins with a key between the 3rd and 4th so as to not put it on backwards. I'm guessing that the additional wires are activating something on those pins that registers the state of the fan.
I have no idea why these non-identical fans have identical part numbers, but this is troubling to say the least. I was very close to replacing the system board or the entire server all together.