I have an 08 Accord Coupe 3.5l V6. Originally when I bout it it had some codes cleared that eventually popped back up (P0155 - B2S1, P0135 - B1S1, P0420 - CAT).. It wasn't affecting the power or rough idle at all, I looked into it and the wires seemed fine so I left it alone. Also if I unplug the battery, the codes are gone until the 2nd start up..which I was doing untill I addressed my parasitic drain..

Finally I got tired of the light staring at me, so I decided to dig further and address it. Scanned again, now it's showing P0161 - B2S2, P0141 - B1S2, P0155 - B2S1, P0135 - B1S1(all heater circuits) & P0498 - EVAP purge valve control circuit low.. I checked my fuses and even swapped them to be sure, all good.. the wiring looks fine. (Both sensor 1's are newer and probably replaced recently)

I'm wondering if it is wiring? Or could the EVAP be causing all this.. I find it hard to believe that all 4 of my O2 sensors are bad..

 

I don't think a leaking EVAP purge valve would cause a heater circuit code, but you should pull the purge valve to see if it is stuck open where you can blow air through it. Replace if the evap is stuck open.

The heater circuit is pretty easy to test with a volt meter or test light. Volt meter is a safer choice. The O2 sensor should have two wires that have identical colors. One of those wires is the 12V source. Unplug the sensor and connect a volt meter from one of the pins on the engine harness side to a good ground and use DC voltage mode. Turn the key to the II position and see if you get 12V. If not, try the other same colored wire. You just want to see if the heaters are getting 12V.