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2000 Toyota Celica

Repairs and maintenance.
Check engine light on for about 4 years (6,000 miles, I don’t drive that much). I bought the car in a Sherriff’s sale in Tennessee, dope dealer confiscation. The car is peppy and runs good. The first time I filled it with gas I put low octane 87 or 83 in it and within 10 miles the check engine light came on and stayed on. I freaked out and pulled into an auto parts store and asked if they could diagnose my problem. They read the computer and told me it was the oxygen sensor. And it would be OK to drive. I’ve changed spark plugs, used 3-4 bottles of injector cleaner and occasionally the check engine light will go off and stay off for a couple of hundred miles, then it comes back on. Each time it comes on I have the auto parts store read it for me and it is always the oxygen sensor.
My question is what function does the OS preform if I still get 36 mpg?
TY
Dan

@99dragons‌

Please post the exact code

example p0130

If the oxygen sensor heater circuit is faulty, it will have no effect on driveability or fuel economy

You can stop using the fuel cleaner. It’s got nothing to do with the oxygen sensor

When it’s time to buy a sensor, get either a genuine Toyota part, or at least a Denso. Denso makes the part for Toyota

The O2 sensor before the catalytic converter measures the amount of oxygen in the exhaust gas so the computer can make adjustments to the fuel trim.

The O2 sensor after the catalytic converter monitors the catalytic converter’s efficiency.

Sometimes O2 sensors can become lazy. This means the voltage output from the sensor slows down or stops altogether.

Usually when an O2 sensor fails the computer will go to default value voltage so the vehicle can still be driven. This default value will cause the engine to use more fuel. Because if the default value were to cause the engine to use less fuel, that could cause the engine to overheat or damage the engine.

Tester

The fact that the car gets 36mpg makes me think it’s the upstream sensor heater circuit

If it were a heater circuit the Check Engine light would be on all the time.

A lazy O2 sensor can cause the Check Engine light to turn on intermittently.

Tester

Thanks for the input.
Can the upstream sensor heater circuit work intermittently?

yeah, the bundle of coke can dislodge, causing the package of weed to interfere with the sensor. common problem in dealer cars…

I was wondering why, when I went to pick up the car from the Detailers that all the workers were sitting around with a jumbo bag of Dorito’s in their laps, and beer cans all over the floor.
They said that I didn’t owe them a cent, but I still don’t know why they all were laughing so much.
I think there may have been a fire there because the shop was full of smoke.

Yosemite