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Open Loop/Closed Loop Question

Hi all!! Just curious.

Do cars switch to Open Loop when in Park/Neutral?

No, they switch into closed loop when the car warms up enough to switch. Doesn’t matter what gear its in. I believe that some go open loop at full throttle but I think that info is only for older ecu controlled cars.


@Mustangman Thank you!!

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How long should it take for a car to switch to closed loop on a cold start??

Late model cars with heated oxygen sensors, no more than a minute or two.
My 2017 Hyundai Tucson takes about 45 seconds.
Earlier models, like the 1988 Accord I used to have, can take several minutes, depending on whether they are driven promptly or left to idle.


@circuitsmith How long would you guess it should take for a 2011 Toyota Camry LE 4 Cylinder?

No more than a minute or two.

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Maybe 2 minutes if it is a cold day…

The faster it gets to open loop, the better the fuel economy and the lower emissions the car produces…

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After an engine is started, there is an EPA-specified upper limit on the time to transition from open to closed loop. I recall it’s specified in a way allow for differences in engines. I don’t remember if operating conditions were part of that spec.

[Updated to switch the open and closed terms. I accidentally wrote them in backwards]

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@circuitsmith Can a faulty O2 Sensor work fine when immediately switching to closed loop but then start to malfunction and send incorrect data when the car reaches operating temperature?

O2 sensors don’t work when cold so they aren’t used for open loop control. That is the definition of “open loop.” The loop is closed when a down-stream sensor provides accurate information that allows the controls to adjust.

The open loop control uses a look-up table capable of running the engine without the O2 sensor.

@ArgosNoble maybe you should cut to the chase and describe the problem you’re having.
Give us make, model, year, mileage, symptoms, trouble codes, scanner readings, etc.