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2016 F150 Engine 2.7- A/F oxygen sensors stuck ON

  • forumoto
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15 Mar 2020 00:07 #38368 by forumoto
I have come across this work, whereby the two banks A/F sensors stuck ON, when car starts and idle for 1-2 minutes. I have trace for any intake leaks, and did other checks but I could not get the trouble area, am wondering the sensor could be an issue but I ask again, how can the two sensors go bad suddenly, I attach screen shot of the freez data and fault code . Thanks for your support

Christ De Way Maker

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15 Mar 2020 06:27 #38370 by Tutti57
I am having a hard time reading the data in the images. When you say stuck on, do you mean the signal voltage on both banks is fixed high? If so, are you able to pull a vacuum line and see if it goes low, lean?

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15 Mar 2020 07:05 #38371 by jreardon
The "Evaporative System Vapor Pressure(Kpa)/(psi)" reading of -4.05 Kpa while Commanded Evaporative Purge(%)" is at 0% may indicate leaking Purge Valve. Negative means vacuum right? I'm not that familiar with that PID.

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15 Mar 2020 08:08 - 15 Mar 2020 08:09 #38372 by Tutti57
That makes sense about the purge. You can try pinching off the purge line and see if the fuel trims get better. I would expect this to be show like vacuum leak though unless the canister is full of gas, unless it is high voltage on A/F sensors? I just can't read the data to know if it is rich or lean, ha.

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Last edit: 15 Mar 2020 08:09 by Tutti57.

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  • Tyler
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15 Mar 2020 12:17 #38378 by Tyler
If your data is correct about there being 4 kpa of vacuum in the tank, then that's definitely a problem. :lol: That's 16 inH2O, which is a TON. Maybe have a look at the fuel tank? See if it's sucked in.

As suggested, disconnect the purge system and recheck trims. Or, give the purge valve a solid whack with your flashlight. ;) Remember that this is a turbo setup, and thus has to have two different ways to get purge flow into the engine. One under vacuum, and one under boost.

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