In this video I show you how to replace a pre-cat o2 sensor, also known as an air fuel ratio sensor on a 2012 Mazda 3. This is the part that needs to be replaced when you throw a P2243 and or a P2251 engine code.
its the first parts to be replaced if all the wirings and connectors are good but at some reason where as the a/f sensor PID is within specification then the main parts to be replaced is the PCM.
Hi, I had same code. Changed it out. Was fine then after 1 year, it comes on. P2251.. then dissapears with no reset. So I'd recommend reset a few times before changing straight away
Same problem, 2008 SP23, changed 2 x O2 sensors because that's what they kept telling me was the problem, second one was original, because they said the aftermarket sensor was the problem, still spits a fault light straight away. Roughly $1k wasted on getting the sensors changed.
@@caseyjones4011 I changed mine myself and bought the sensor cheap so cost wasn't a problem. Mine is obvious a short in the wire but too much of a pain to mess with at 17 years old. I failed emission test but started moving wires around and was able to get the check engine light off long enough to pass test a few days later. Check engine light came back on and I will live with it. I must of messed wires up when I had to fix air conditioning wire which was in the same bunch because right after that these codes popped. They also say that clip where it plugs in could be a problem on the upstream sensor.
