check engine light

[Kubna]

I own a 99' 540i and the check engine light came on. I took it to the dealership (New Century) in california. The dealership kept the car overnite. They did a tune up, inspection, change belts etc. the main reason for taking it there was for a diagnosis on the check engine light. So the do all the servicing and stuff but say that the diagnosis was unsuccessful, and they would need several more hours to determine the cause. The SA suggested that it was probably the fuel filter, and that I buy one(filter) change it myself (we had discussed me being mechanically inclined) and the light would probably go off. Needless to say it didn't. I even disconnected the battery which caused the light to go off for a day then come back on. So my question to anyone reading this is does anyone know what the hell it could be. My last guess is to change all the O2 sensors. But since they are so expensive I wanted to ask you guys first before spending more than $400 for 4 O2 sensors! PLEASE HELP! ghead

[Dirty_Tool]

Check engine lamp can be so many different things. Do you have an invoice with the fault code/s that they pulled up during diagnosis? That might help some.

[Speedfreak]

Doesn't sound like a very good shop. You might want to buy a fault code reader.
I bought one and I knew what was wrong before I even took it to the dealer.
This most likely isn't going to be the only time that light comes on.
A reader is cheap insurance.
Pat

[Torque]

Take it to a place that has a updated OBD II scanner, and have them scan it. This scanner is also the only way to turn the check engine light off... so even if you changed the part causing the problem, it will not go out by itself.

ps. Check engine could mean:
- Fuel filter
- misfiring
- egr valve
- many many other things...

[Kubna]

I do have a fault code reader, but it is for all other 5 series except for the 540i. I knew this when I bought it, but the reason I went ahead with it is i couldn't find any fault code readers for the 99 540i. I figured some of the codes should be the same as the other 5 series. Anyways, if you know of any fault code readers for the 99' 540i please let me know.

[EXtech]

Jesus, your dealer and service advisor are one conglomeration of buffoons. Your check engine light is not on because of a fuel filter. In all of my years in the automotive business I saw one case of a fuel filter causing a check engine light and that was because the owner's exwife put sand in his gas tank which clogged the fuel filter (and the pump, injectors and fuel lines) thus triggering a CE light. Stop wasting your money or jumping to any irrational conclusions. I'm not sure of the mileage on your car but here are my suggestions. The first place that I would look would be the crankcase vent valve, aka pcv valve, aka oil seperator. With the engine running at idle, raise the hood and pull the dipstick. If you hear a honking, whining or groaning type of noise then you have a faulty crankcase vent valve. On some models there is also a small s-shaped vacuum hose connected to the ccvv that may also be deteriorated. This usually occurs around 45k but I have seen it as early as 35k and late as 65k. I would do a complete intake reseal which would include the ccvv and gasket; the front plate gasket and the intake to cyl head gaskets. Of course I'm assuming the dealer (the same one who told you the problem was the fuel filter) checked the easy and obvious possibilities like intake air boots, oil cap, gas cap and electrical connections. The other big problem on these V8's are the valve cover gaskets leaking oil into the spark plug chambers. You can remove the black plastic covers (2- 10mm bolts), remove the coil packs (2- 10mm bolts at each plug) and check for oil accumulation. If this is the case then you will need to replace both sides. If neither of these are the culprits then I would look to the catalytic converters (mainly if you have 75k miles or more). Usually when these are failing you can get under the car and whack them several times and here a rattling sound (but not necessarily always). These are just some common causes of check engine lights on the V8's. Yours may have some other problem that needs diagnosis by a competent shop.

[Kubna]

THanx, for the advise. I ran the engine at idle, pulled the dipstick and all i heard was a gurgle. No honking, whining or groaning. It just souded like the oil slopping around. I assume this is normal. Spark plugs are cool too, not any oil in that area at all. You know off anything else I could try? Thanx in advance.

[CosmosBlack]

What kinda symptoms do you have? That would help with diagnosis.

I had a MAF sensor fault that triggered the check engine light for some time, which led my mechanics to beat around the bush replacing expensive parts, including the oil separator, throttle body, and finally the MAF sensor. You might wanna check that...