Got the SES light on during a road trip last week. Had my little elm device with me so I just plugged it in on the go and read the codes. Only one was P0401. I cleared it (still on the highway) and drove another 5 or 6 miles before it came on again. Car acted totally normal otherwise. Starts and runs fine. It does seem to idle a bit rough when the code is on, but not terrible.

I looked at the live data using Dashcommand on my iPad. The map sensor is staying about 35 at idle and only fluctuates during rpm change. The O2 sensor caught my eye however. The range on the dashcommand "gauge" is 0 to 1.0 volts. It bounces rapidly all over that range at idle. Rarely holds still. Is that normal? What should the O2 sensor read at idle and at highway speed (2000rpm)?

Everything I've read so far on this code seems to indicate that egr is the last thing to replace and it is rarely the problem. So I'm looking for vac leaks etc. but the O2 sensor is standing out to me. Any thoughts or input on the normal O2 readings?

I just had the same problem. I removed the EGR valve, cleaned it with carbon cleaner and then let it soak in about 3/4" of carbon cleaner for 15-20 min. Put it back on and all is good. I did use a Bluetooth ELM reader and checked afterwords and the code went away. Takes around 2 min to remove the EGR valve. Be careful not to drop the 2 nuts.