ERROR CODES: PO581, PO593, PO420 AND PO113

2007 Dodge Caliber • 150,000 miles

I bought this car used about 3 weeks ago. Its running fine. This morning I crank up and the engine light is on. I took it to my local hometown mechanic and he hooked it up to a diagnostic computer. The following error codes were given: PO581, PO593, PO420 and PO113. I am needing to find out exactly what they mean and if hopefully these are easy repairs. Any help would be really appreciated.
September 5, 2012.

Check your battery first if it's low or in bad shape it wil give codes like this all at once. A cople of them may be due to either a bad catalyst (convrter) or o2 sensor problem. Try the battery first have hthem cleaered and see if they come back. One of thesee could be a bad ground, pcm or intake air sensor.

Sep 6, 2012.