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Good Afternoon Everyone. I wanted to put "this" out there to see if anyone had any other ideas or have experienced similar issues. The Topic is on the Readiness Monitors for Emissions.

I have a '13 Focus ST with a catted Depo DP with a defouler on the downstream O2. Currently have an Unleashed E30 Tune on the car.

The problem - I have 2 Readiness Monitors that will not check in; 02 & 02 Heater. I am allowed only 1 monitor to not be active and still pass emissions.

What I have done (in no particular order) - Put the car back to the stock tune; put the E30 tune back on the car; replaced both the Upstream and the Downstream 02s; replaced the battery; replaced the battery monitoring sensor; I have actually unplugged both (at different times) 02 sensors to see if I would get a check engine light, and both times I did get a light (yes even with the E30 tune installed); I have an app that allows me to monitor the voltage that both 02 sensors are getting, and they are in line with what would be normal; I have no other check engine lights; I have driven the car many many many miles over many many months; plenty of warm-ups; I have also cleaned the MAF sensor...

Any thoughts on this would be appreciated. Thank you!
 

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Do you have a wiring diagram and a digital multimeter?

My first check would be to see if there is voltage between the heater and ground pin of the O2 sensors with the ignition on. I don’t think the engine has to be running, the purpose of the heater in the O2 sensor is a faster warm up of the sensing element.

Be sure to stay away from the signal pin, an analog meter doesn’t have enough input resistance and can short out / ruin the sensor, or so I’ve been told. One might get away with it using a digital meter, but why take the chance? That reading comes up nicely on the scan tool anyway.

It’s a place to start. Good luck and keep us posted.
 

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have an app that allows me to monitor the voltage that both 02 sensors are getting, and they are in line with what would be normal
Just to be sure, this is the + / - 1 volt or so that the O2 sensor is switching off and on, correct?

Last time I chased an O2 sensor problem it was on a pre-obd 2 Pontiac so my knowledge may be out of date.
 
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