P0156 - Heated O2
Sensor Circuit Malfunction (Bank 2, Sensor 2)
Codes can be intermittent if the problems are intermittent, so it's not unexpected. The code for your O2
sensor is probably a sign that the sensor is starting to get lazy or the heater is wearing out. You can inspect the wiring, but if it looks good I would just replace the sensor (it's the downstream sensor for the front bank). Have you tried replacing this sensor before?
codes can also be difficult to track down. I'm guessing you had a P0455? That one can be a bad gas cap seal, so it's a good idea to replace the cap. It could also be a purge solenoid that is sticking, or possibly a bad fuel tank pressure sensor. The EVAP
leak monitor only runs under specific circumstances, so if you use the car a few times after setting the code (but before the leak monitor can run again), the CEL
will go out. When the leak monitor runs again, then the CEL
will come back on. So in that sense it might seem like an intermittent problem, but it might not be actually.