Chorban got information that pretty much confirmed Vigil's statements about the Keepers. Including that they seemed to be waiting for a signal. But there is no mention of him being able to figure out they were blocked from receiving that signal.
In the end, manual override is what they ended up doing. But (for whatever reason) Sovereign had to do it himself. No it's never explained why. I can only surmise that Saren was not compatible with whatever interface the Keepers use.
Maybe it makes no sense that Sovereign couldn't run a diagnostic on the Keepers. But then, it makes even less sense that the Catalyst can't. Or that the Catalyst required them to open the relay to begin with... 
We also know that Chorban's equipment is primitive compared to the Reapers. Since we aren't able to get any decent research into the Keepers, our tech that is capable of scanning them is very limited on top of the fact that they were designed to prevent scanning. The Reapers of course would already be aware of how all of that works.
If we assume that Prothean interference changed enough so that Saren did scan them for Sovereign and didn't get any decent readings that still doesn't explain why they didn't just do manual override at that point. Searching for the conduit is just stupid when you haven't tested the Citadel to make sure it still works.
It makes even less sense that the Catalyst couldn't have figured all this out or even just triggered the Citadel itself, but I'm working purely on ME1 established lore to point out where it made no sense. It gets 10 times worse when we start including the later games =P
In either case my whole point is that I just pointed out a lot of things in Mass Effect 1 that make no sense, but every time I do somebody defends the game tooth and nail.
When one points out that the Catalyst also makes no sense, people jump in to agree how stupid that whole scene is(which it is stupid. I don't want to try to claim that it isn't).
That's exactly what you're doing. You're saying we should stop talking about how terrible the ending of ME3 was because some of the stuff in other games is kinda stupid. That's why I called your argument a cop out.
No I'm not. At no point have I said we should stop talking about the ending to ME3.
My point is and always has been that we ought to be talking about all of the bad writing in the series, not just one specific thing. I have stated this multiple times now.
They can avoid future problems with the series' writing if they better plan things out from the very start of it. Taking out the Catalyst(the thing everybody complains about, with good reason) scene entirely doesn't fix all of the problems with the ending, it just removes the problem most obvious to us at the time.