Hey y'all,

CEL came on yesterday. Had the guys over at Advance Auto run it and P0135 came back. AFAIK, Bank 1 Sensor 1 is the first passenger side O2 sensor. I know recently I took out and put back in the O2 sensors while reseating the exhaust. The engine doesn't run rough in any way. For now I just reset the battery (disconnect negative, wait, reconnect. This may not seem like a fix, but one time my Vic was running on a very low idle, a battery reset fixed it) to reset the sensors (ABS codes also came back, but I know why that happened; they just needed to be reset). So far it hasn't come back, but if it does, would anyone know why?

Thanks.

So P0135 is Oxygen Sensor Heater Circuit Malfunction.

Either the heating element inside the sensor isn't working well/at all or there's an actual issue on the heater circuit itself; so you may want to check that the circuit has power at the connector, and there's no damage to the harness.

How far have you driven since you disconnected the battery? It may have not been through enough drive cycles to code out.

Car hasn't left the driveway since then. Will most likely take it out this weekend and will see if the code comes back.

Drove it today, CEL came back on, assuming O2 sensor. What should I do? Replace it? No rough idle or poor performance.

If the heater element in it has failed, replacement is the only option unless you enjoy looking at the check engine light.

Alright. Will check connections and try switching sensors around to narrow it down to replacement.

Actually I found out why I was having the issue: the O2 sensor wasn't even plugged in. I'm a certified idiot.