My Evo started throwing codes p0141 (O2 sensor heater circuit malfunction Bank 1 Sensor 2) and p0136 (O2 circuit malfunction Bank 1 Sensor 2).

I am catless, but I have a sparkplug antifouler in front of the O2 sensor. I've been running this set-up for about a year and a half with no problems.

I cleared the code, and drove around. No problem. But the next time I started up the car, the code came right back.

Today I removed the rear O2 sensor and checked everything. Didn't notice anything strange, wires are OK, no leaks. Not sure what else to check. I put a second antifouler for good measure.

I cleared the code, drove around. No problem. Once again, the next time I started the car, the code instantly appeared.

Any ideas?

 

if it is coming on on startup, the computer is seeing something within the "fail" parameters. alot of things could affect it, being cold start vs. what the sensor is reading, or a voltage discrepancy. it could also be related to something else failing in the coldstart system like an ect or thermostat staying open, running too rich and throwing the o2 readings off. the rear o2 sensor is supposed to read relatively high millivolt readings indicating clean exhaust. 700-900 mv . the sensor itself could be bad also. good luck.