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My 2012 Volvo C30 T5 has been having a recurring engine code P2196 (O2 Sensor Stuck/Biased Rich) for some time now. It has popped up on four or five separate occasions. I usually clear it, but one time it went away by itself during a 2-hour drive at highway speeds.

At first, I noticed that it seemed to pop up when going through a touchless car wash, specifically at the very moment that the underbody was sprayed with water. This happened twice. I thought maybe a boot was torn and the water was causing a sensor to report a value out of spec. But, it also popped up a couple of times while idling or driving slowly, which is what I do when I’m going through the car wash, so it could just be linked to idling/driving slowly.

Context, I typically do lots of city driving and little highway. The user manual recommends premium, but states that regular fuel will not damage the engine. I had been putting in premium, even 94 at one point, to try to clear the issue, but to no avail. One day, I filled up with regular 87 in preparation for a 2 hour trip at highway speeds. To my surprise, the light went away during this drive. Not sure why.

Anyway, all this seems to point to a bad O2 sensor. But, when I did an “O2 Sensor Test” with my OBDII code reader, the test passed.

What could this mean? Should I try replacing the upstream O2 sensor anyway?

More context: ODO is at 150,000km (93,000 mi). Oil is always changed on time, with synthetic . Air filter looked fine last I checked, and I think the spark plugs were changed recently, but not sure about the fuel filter or PCV system. I do lots of 10 minute trips from a cold start, we do have long cold winters here, and the car is garaged most of the time.

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    Welcome to Motor Vehicle Maintenance & Repair! Commented Apr 20 at 11:02

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The O2 sensor is covered in soot and other deposits. The improvement with highway driving and use of regular/87 octane is a dead giveaway. The lack of highway driving exacerbates the problem. Replacing the sensor(s) will eliminate the problem only for a time, then return before long (unless, perhaps, the sensor has 150k+ miles).

What is the car's mileage? Deposit buildup gets worse with age, but happens routinely even on a brand new car with very low mileage. How is the condition of air filters & fuel filters, spark plugs & wires, PCV & EGR valves (if applicable), vacuum hoses and other tune-up parts? Has the motor oil been changed regularly? You've already mentioned city driving. How about short trips under 15 minutes from cold startup? Do you live in a climate with long winters? Is the car garaged? All of these factors accelerate deposit buildup.

There are a number of additives you can use to clean up an engine, which I I've used with great success if you're interested. It is, however, most cost effective to start with the basics and provide this forum with more complete information.

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  • Thanks for your answer. ODO is at 150,000km (93,000 mi). Oil is always changed on time, with synthetic . Air filter looked fine last I checked, and I think the spark plugs were changed recently, but not sure about the other components. I do lots of 10 minute trips from a cold start, we do have long cold winters, and the car is garaged most of the time. Anything else I could try besides (or in addition to) replacing the sensor to prevent this happening again?
    – ivorysoap
    Commented Apr 22 at 4:38
  • LIQUI MOLY Truck Series Complete Gasoline System Cleaner. With extra passengers in the car for weight, run the car hard for two hours. Pump the the gas pedal 10 times to the floor at roadside (in neutral of course), then shut off immediately for 5 min. Start, then heavy acceleration all the way up to full throttle, followed by a period of 15 minutes at a very steady, 100 kph on the highway. Repeat this cycle for at least a half tank. Continue to treat the gas for five tankfuls. Change oil when finished.
    – Carguy
    Commented Apr 23 at 0:06

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