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trouble code p0172/ o2 sensor

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grey 98 s70

trouble code p0172/ o2 sensor

Post by grey 98 s70 »

I have a dumb question. I have a 98 Volvo S70 with 235,000 miles and still going strong but my check engine light came on. I had it hooked up and it gave a trouble code of P0172 {Fuel mixture too rich}. My engine is the non-turbo engine. Would replacing the O2 sensor be the first place to start and by the way, where exactly would it be located.

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Post by pageup »

In so many cases... the O2 sensor is rarely replaced, (and IGNORED!) but it really needs replacing at 50K mile intervals (imo) for optimum results. This sensor is one of the most critical items in maintaining a proper closed loop fuel mixture management scheme. Without a good O2 sensor, your system's only working at half it's potential, or less.

So... yes, absolutely, replace that O2 sensor! Unfortunately these things can be a dog to get to because they need to exist downstream of the exhaust output of the engine, which nobody ever cares to deal with. To find it, follow your exhaust pipe from the engine (exhaust manifold) until you find something that looks like some kind of R2D2 Spark Plug thing with a single or multiple wiring connection. Some will have 1, others will have 3 wire connections with a plug.

Depending on the location, it can be a real pain to remove... but in some it's not too bad. And I have absolutely no idea what the underside of a 98 volvo anything looks like. If you have good lateral access, then a simple box end wrench will work, otherwise, you would be wise to purchase the special O2 sensor socket that'll fit it (available at most auto parts houses /pep boyz/autozone/kragen/advance/chiefs for about $19).

I'm no expert, but this is my experience. The engine's fuel management system uses this things' output signal as it's final check for determining the amount of fuel sent to the engine. Without a good O2 sensor, your vehicle's kinda toasted. :twisted: .... and with that kinda mileage, if you don't know if it's been replaced recently, it probably needs it anyway.

After all - a computer said you need it right?
8)

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