2002 325CI- Service engine soon

With 37,500 miles! Any chance that its something simple? I just passed emissions test a few weeks ago. I checked the gas cap, but that was fine. I do oil changes myself so I don't reset
the oil change indicator.(Low mileage) That can't be it?
Joe
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It is a problem somewhere with the emissions controls. As the car is still under warranty, take it to the dealer.
A common problem is one of the O2 sensors, but the code reader will tell them which one and what is wrong with it.
Jim

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Thanks Jim
Took it to my friendly neighborhood Autozone. Code reader showed P0155. Code in my Bentley manual: "Heater Circuit, Bank 2, Sensor 1" Autozone tech said check connectors, I shouldn't be having a problem with the O2 sensors at 37,000 miles. Hmmm...... Joe
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Those things are easy to break. As for 37000 miles, it all depends. Yes, it is easy to connect them wrong. However, like most hardware devices, they fail whenever they fail. Mine was replaced long before that mileage.
In any case, O2 sensers are covered under warranty.
Jim
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"> >> A common problem is one of the O2 sensors, but the code reader will tell

I disconnected and then reconnected the sensor and after a couple of startups the light went out. I hope it stays that way!! Joe
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It probably will. But, since in the US, this equipment is covered by law for 50,000 miles, you really have nothing to worry about.
Jim
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It really says, P0155 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
The O2 Sensor has a heater element in it that helps it keep the air/fuel mixture within a specified range. Your code is telling you the heater portion of the O2 sensor is not working. Since this is an emission related problem, and the emission system is still under warranty, I'd let the dealer take a shot at the repairs. Having said that, replacing the O2 sensor is much the same kind of job as replacing a spark plug. You _might_ need a special socket wrench, but it is also possible to replace this component with an open-end wrench, or even a box-end wrench. (Obstructions within the arc of the wrench will dictate the need for a special tool.)
Your car has a split exhaust manifold, one portion bolted to the forward 3 cylinders and the other portion bolted to the rear 3. The sensor you need is the rear one. Both of these sensors will be in the exhaust manifold before the CAT. You will have O2 sensors in front of the CAT and one or more after the CAT.
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Could be a coil, but I'd think you'd notice, it isn't smooth on 5 cylinders. Warrantee right? No problem.
R / John

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