I got a check engine light with a P2A01, so a bank 1 sensor 2 on the O2 and noticed the check engine light flashes when driving along with a rough idle. After a few hours with a pipe wrench I replaced the sensor and everytine I started the hummer the check engine came on and I got two different codes repeatly. P36 and p54, I sent the sensor back and will try another brand. I tried cleaning the old sensor with some MAF cleaner and put back in. I'm not getting any check engine errors but the rough idle and flashing check engine are back.

I was looking at realtime b1s2 voltage and it hangs around .85 to .775 compared to our h3 which seems like it bounces all around .15 to .8. Is it normal for a .85 on a h2 or is that the running rich and the rough idle, which is what i figure.

strange im not getting errors but the flashing check engine . I will try another sensor just wondering if anyone else has some knowledge on reading that blue driver obd2 with the sensor voltage. I did notice on the first sensor i tried it sat around .45v but was throughing check engine lights as soon as the keybwas turned.

2006 h2 hummer

 

you may have a wiring issue and not a sensor issue, if both sensors, new and old are doing the same thing then look at the connectors and wiring on the heater side of the O2 sensor.

the flashing engine light means the sensor is detecting a rich mixture that can damage the CAT

MAF airflow is high, was the engine at high idle, cold start?

Neal

 

mass should be around 6 on idle
rear o2's seem to be behaving like your cats are shot.

 

Sensor 2 has nothing to do with fuel trims and nothing to do with how the truck will run. Its only for the catalytic converter to monitor its efficiency. It should almost always read "rich." with a properly functioning catalytic converter(I know its sounds counterintuitive). The code you have is for the heater circuit within the o2. Start by checking the fuse for the bank 2 sensor 2 heater circuit. If that's fine, load test your wiring and connections with an incandescent headlamp. If all that checks out, it needs a pcm.

It is possible for the wiring to short or the o2 sensor to fail in such a way that it fries that circuit on the pcm even though its a ground control circuit. Its weird but I've seen it happen.

If a catalytic converter is bad/below efficiency, sensor 2 will replicate the oscillations of sensor 1. If it's working, you will see a steady rich(less oxygen) reading or slow oscillations. They will not oscillate at all if its not heating up(ie... the heater circuit is bad)

 

Ok so i returned the new sensor and exchabged it for a Bosch at 3x the cost but before i installed i ran the old oroinal sensor and its almost like it wouldnt stary and would chug and stall on a warm day at 20 celius.
i put the bosch in and seems to start ok and idle ok. Took it for a short drive and no codes popping up no flashing engine light. It kinda looks like the original sensor went and the new cheap one gave me different b1s2 errors.
i think i understand now the B1S2 role not sure why i saw so many videos saying the 2nd sensor dictates. I breifly notived the B1S2 kinda hanging around .75 to .885 so this would be a little to high ? Meaning cats on their way out.
is there anyhting you can add to try abd clean them up a bit or just wasted money.
My MAF sesnor should be around 6 or 7 when in idle?

i thought thry sent a used Bosch sensor as it looked heated and had sone grease on the threads, but thats whatbitnlooks like in the amazon pic

 

That voltage is fine for sensor 2. If your cats are bad, it will follow the oscillation of sensor 1. However they could still be plugged up. You could try unplugging all of the sensors/ Then disconnect the exhaust from the header flanges and see if it will run right in open loop.