My 325i and questions...

[325iBiatch]

Hello all,

I have never owned a bimmer until about a month ago... I've been reading about on this forum, and between that and a service light that came on, I have a few questions....

1) What exactly is a subframe? (One thing I've never thought of looking up in the past...)

2) My "Service Engine Soon" light came on... I went through all the things, and my thermostat(??) is reading constantly at 122+ degrees F.... How much does the thermostat cost to replace about? Is it really the thermostat, or could it be something else?

Thank you all for your help...

~321iB...

[Manolito]

1) I never really thought about that one. Very few passenger vehicles have full-length frames. They used boxed stampings spot welded to the car to stiffen the body. The heaver metal assemblies to which the suspension and differential are bolted are, I think, called subframes.

2) What do you mean by "went though all the things" and how do you know that your water temperature is 122F? If that is true, it is way too cold and will cause the car to run rich. You need a tool like a Peake tool to read the codes to determine exactly why the Service Engine Soon light is on. That light indicates a non-fatal error, meaning that the fuel control is still running closed loop as it should, but some minor thing is amiss.

I just read out the codes on mine and it complained about nondescript problems with the catalytic converters and fuel vapor control. The catalytic converter error simply means that OBDII does not know what the problem is but the engine sensors are not responding properly to fuel adjustments. Could be worn plugs, old sluggish O2 sensors, leaking exhaust manifold, lots of things. The fuel vapor control code probably means the wife left the gas cap crossthreaded once.

[325iBiatch]

....water temperature? I think maybe I meant to say thermometer... It has to do with the temperature outside.... Sorry about the confusion.... 122F would be a pretty warm water temperature though, right?

[Manolito]

The thermister that measures outside temperature that you see in the on-board computer is located in the the air duct that goes from the air dam up front to the diver side front brake. The reason that it measures and reports outside temperature is to alert you when the road temperature gets near freezing so you know that there might be ice on the road. When it is hot outside, that temperature gauge tends to exaggerate a bit due to its proximity to the hot road surface. If it always reads 122F, check the lead and plug, but the thermister is probably damaged.

The thermostat is a temperature activated valve on the front of your engine that throttles the cooling water flow through your engine so that the engine operates at the appropriate temperature. That cooling water is normally around 200F.