I got a code 153 out of the A2 socket on 850 NA, "153 Rear HO2S signal". I read where sometimes these can be cleaned and function properly so I tried. Put it in a jar of gasoline and let it sit for a week, swirling it around regularly. Removed it and bench tested tonight. I got 3.2 ohms on the heater element which I believe is in range. However I'm confused on the voltage test. I do not have access to a graphing multi-meter, or even have min/max on mine. Heated the sensor tip to 600+ degrees and got a reading of ~.47 volts. From what I've read online it appears that it is not responding quickly enough, as when I removed the torch, it took a long time for it to respond with decreasing voltage. Am I correct in assuming that it should start dropping (almost) immediately when heat is removed ?

Thanks, Al
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Optimist - half full, Pessimist - half empty, Engineer - The capacity is twice what it needs to be.

bosch o2 sensors are about 80 bucks on FCP. I personally would just trust the fault code.

This is more screwing around on my part than anything. I'm not currently driving this car. Bought it cheap ($300) and am working through it fixing it up for my daughter.

Thanks dg
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Optimist - half full, Pessimist - half empty, Engineer - The capacity is twice what it needs to be.

Without a graph, it will be hard to verify. 600F should be over the max temp for the sensor which could account for the slow decrease in voltage.

Was the sensor really dirty? Have you tried putting it back in the car and letting the computer test it?

A cheap ELM327 scanner along with a smart phone or PC should be able to chart the sensor. But that is also a large learning curve. Know anyone with a scanner that works with OBDII, the early year version?
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My back feels better when I sit in a Volvo seat

I reinstalled the cleaned up HO2S, but alas, there was an immediate DTC 153 after a short test drive. Oh well, worth a try I guess.
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Optimist - half full, Pessimist - half empty, Engineer - The capacity is twice what it needs to be.

I went to FCP to get the part number for OEM version. Then I compared the price of the same part number on Amazon and bought it there at a much lower price.
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My back feels better when I sit in a Volvo seat

"Was the sensor really dirty?" Hard to say, I really didn't notice what it looked like when pulled.
"Have you tried putting it back in the car and letting the computer test it?" That sounds like a really good idea, I think I'll try that tonight.
"Know anyone with a scanner that works with OBDII, the early year version?" I have an OBDII, but don't think it has the advanced capabilities, at least I've never found them in the menus.

Thanks Klaus
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Optimist - half full, Pessimist - half empty, Engineer - The capacity is twice what it needs to be.