A couple questions, please. Got a '10 Sierra, 5.3L. Been getting an intermittent CEL. And when I say intermittent, it's really about 10-12 months apart, happened twice. Local Chevy dealer service tech reset CEL light, both times. Right bank, rear O2 sensor, both times. Last instance, 2 weeks ago, reset and hasn't come back on. I had scheduled a visit for today to get the sensor replaced, they talked me into just leaving it alone since the CEL was still off. When they reset the CEL last I asked if the sensor was still showing as failed, they said yes. Which leads to Q1. If the sensor was hard failed would they have been able to reset the CEL light. My limited understanding of this computer crap says, no. So what is it yes/no? Q2. Id like to buy a code reader. From my sparse research it appears that it takes a multi function reader to access all the vehicle components, ABS, Airbags, 4WD, engine codes, etc. I'm looking in the $75-$100 for a reader. What is a good unit in that range? I just assume that isn't going to access all the aforementioned systems, only engine codes, right?