This may sound strange, but if your battery is over 4 years old, replace it. Here are some articles I wrote on Monitors and Drive Cycles that explain why.
http://repairpal.com/Drive-Cycle-Issues read section 4 about the Oxygen Sensor readiness Monitors and how it needs a good Battery or it won't run, I have replaced lots of Honda and Acura Batteries to deal with with this Monitor Problem and with really good success. I do Smog Failure and Smog Problem Diagnosis in a Gold Shield Station in California.
Hello... I have a Hyundai Sonata. The battery was replaced 8 months ago (or at least I hope it was b/c I paid for it). It was recommended by the dealership where I had my car serviced.
Anyway, fast fwd to today Feb. 2011... I've taken my car in for its first smog test - and it failed due to 3 monitors not being ready. One monitor is the Oxygen Sensor. I've got the Drive Cycle from the dealership - and tired that. Per the smog station.... the 3 monitors are still 'Not Ready'. I tried driving it prior to getting the Drive Cycle diagram -as has been recommended here on RepairPal. That didn't work. Now, the Drive Cycle didn't work either. It's impossible to do it exactly b/c I don't have a stop watch to time for 15 seconds & 1 minute requirements in driving, slowing down, speeding up. But I did the best I could. Please tell me if your Gold Shield station can help me. I live in the Bay Area, but I'm willing to drive an hour or two for the right mechanic who can resolve my problem using a dyno & who really knows about these type of monitor problems.