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I looked at a car today with the codes listed above. Slow response from both downstream oxygen sensors. I saw that the heater circuits were never controlled on for both banks. Immediately my Thoughts are if heater circuits are not operating properly then the sensors will not reach operating temp and not function as intended to. I tested the ground control for both sensors at the PCM with the vehicle running. Neither control wire for the sensors were grounding at all. I went ahead and added my own ground just to see what the sensors did and they started operating. I did check the ground for the PCM. At the PCM and it was below 200mv. I haven’t got to do any research on a software update yet. Just wanted to see if anyone has ran into this issue. The vehicle‘s rack and pinion was just replaced and on this vehicle, which involves dropping the engine and transmission assembly (I did not do the job). Any thoughts or insight would be greatly appreciated. Thank you
You'd think they would want to heat up fast, but I would check it driving. I feel like I remember hearing about a similar scenario in a case study or something...
That’s a good thought. From my experience, The heater circuit is controlled on as soon as you start the vehicle. My thoughts were that both sensors going out at the exact same time is unusual also.
I agree, almost every car I have looked at activates the heater circuit on start up or very shortly there after.
But I can't seem to shake the idea that I've read about, heard about or saw a video about downstream heaters not coming on at start up/idle.
OK so I figured it out and I feel like a dumb ass. Instead of going after the O2 sensors I read the codes on all data. If I remember right it stated that the code is caused by a slow response after fuel cut off. I checked my fuel trims while driving and I noticed that during acceleration my fuel trims would go lean. During a hard acceleration I could get them to go rich with plenty of power. I did not suspect A fuel pump problem. Also during the test drive I noticed that the heater circuits work properly. You were right. So initially I went straight for the mass airflow sensor and found that the intake tube was improperly installed allowing unmetered air. Fixed. Thanks again
