Can't figure out what's causing P0345 code!

A couple weeks ago I had been driving my car for about 5 miles when lights came on (check engine, "check vsc", and traction control) on the freeway. It runs ok, but I noticed low idle at 500 rpm at a stop and slight fluctuation. I replaced the camshaft sensor twice with OEM ones, but it did not change anything. Checked the wiring and everything looks to be in place. No recent maintenance has been done. High pressure A/C line was replaced several months ago long before the code came up. During an oil change two days ago, the battery was tested and the report stated that it needed a charge. The tech charged it and must have cleared the codes since they were gone, but a few minutes into driving the car they all came on again. The car runs the same with the sensor unplugged. I have read the code can be from a skipped tooth on a timing chain, but is that possible without having worked on it? What could be the problem?