Yeah, take it in and see what they find. Don't let them just throw 2 sensors at it. The heater outputs are really easy to check. Erroneous O2 codes and some dead heater circuits are nothing new on the later model NGC controllers. I have replaced quite a few PCMs for them. There isn't a TSB for it on that year, but there is a "tech confirmed repair" listed. The newer minivans even have a recall revolving around erroneous O2 codes and a few TSBs for other years and models.
The high voltage code could just be an indication that the heater didn't drop the O2 voltage fast enough. The criteria can sometimes overlap depending on many things. Probably you have no PCM output from the upstrem O2 heater circuits. I see 1 maybe 2 a month on average and we work on a lot of cars.
Last edited by TNtech; 06-28-2013 at 08:04 PM.