pooperscooper

I recently took my 98' taurus (3.0) to have the codes pulled (due to a service engine soon light). The codes said that all 4 of my oxygen sensors are bad.

The light has only been on for 2 weeks and about 1 week ago, the light went out for one day. This seems a little odd, to have all 4 go out at exactly the same time. Is this an electrical problem, or is it actually the sensors? Any advice? Thanks.

tbird100636

What were the exact codes???

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SHOZ123

I agree. There is either a wiring problem or a PCM problem.

If you can trace the wires down on the PCM connector you can back probe the connector and see what the O2s are sending back with a voltmeter. They should oscillate between ~.3 to ~.7 volts.

pooperscooper

Thanks SHOZ123. I was going to do the backprobing, but I didn't now what the parameters were. That will help.

SHOZ123

You should not see 0volts or higher than 1.5V

pooperscooper

Follow UP:

After debating on diagnosing my electrical issues, I realized that a professional would be better suited for the job. I found a guy in Fremont, CA that charged $80. His report found that it's actually a problem with the PCM. He's saying that, although the 02 sensors and heaters are good, the heaters aren't getting the proper signal. He then quoted me $650 to replace it.

I have searched ebay for used pcm's and they seem to be going for about $50. Does anyone know how difficult it is to replace? It seems to be lodged inside the firewall, but I don't want to just rip it out without any input from people with experience. Thanks.

RickMN

Rather than go used, contact one of these places and have them rebuild yours. It will cost a bit more, but will have a warranty.

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I'm a retired ASE Master/L-1 Technician. I still keep current with the latest automotive technology. Visit my blog for cool articles and TSB's: http://www.ricksfreeautorepairadvice.com/