ST165 Code 12 with Wideband O2 Sensor

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ST165 Code 12 with Wideband O2 Sensor

Postby Maet » Wed Sep 15, 2021 12:34 am

I just started getting a code 21 after I swapped out my O2 sensor for a wideband which will eventually connect to a standalone ECU, but in the meantime is there anyway to get rid of the check engine light? I don't have an O2 heater so it's throwing a code.
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Maet
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1988 Toyota Celica

Re: ST165 Code 12 with Wideband O2 Sensor

Postby alltracman78 » Wed Sep 15, 2021 7:15 pm

Your wideband has a heater circuit too, but it works different.
It's the wrong kind of sensor.
You need to have a regular O2 sensor hooked up to the factory ECU.

A regular O2 sensor creates voltage depending how much oxygen is available and sends that voltage to the ECU.
An A:F (wideband O2) sensor changes the amount and direction of current flowing through it depending how much oxygen is available. The ECU sends a specific voltage to the sensor and monitors the current flow through the sensor.

So an ECU set up for a regular O2 sensor can't read the signal from an A:F (wideband O2) sensor.
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Re: ST165 Code 12 with Wideband O2 Sensor

Postby Maet » Wed Sep 15, 2021 7:39 pm

I'm more looking into a way for the ECU to trust the data from the new sensor depite it having no heater connected. I read somewhere that you can put a 5.5K resistor (what the O2 sensor usually has) somewhere to get rid of the light.
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