Unfortunately, there are many problems that do not have their own idiot light, but are lumped together under the "Check Engine" light.
That's disturbing, when you know or at least suspect that something's wrong, but you don't know what.
Obviously, even if you have your own scanner, you still don't know for sure, but wind up going to a Suzuki service center anyway.
On my 2006 Forenza, my check engine light came on when I had a leaky oil filter and my oil was getting low. After driving carefully, for about five miles, my oil light finally came on and I knew I needed to get to a service center, ASAP.
If in the process of doing an oil change, oil was spilled on the lower O2 sensor that can cause a problem. That's been talked about in the SX4Club forum.
On the 2009 SX4, that lower O2 sensor was moved further back, about a foot away from the oil filter, to eliminate that problem.
By 50k miles or a little more, O2 sensors can become contaminated with impurities in the gas and can drift so far out of spec that they are virtually useless.
I'll be changing both of mine, at about 50k miles. Both performance and gas mileage will improve.
Good Luck and please let us know what the dealer finds.
The Shadow (ocala fl)