I recently had the service engine soon light come on in the Z4 after a fill-up. I took it to the nearest service center and the error code was (as you might have guessed) a loose gas cap (though the "check gas cap" light didn't come on, and I don't see it when I first put in the key). I had suspected this and re-tightened the cap, but the dash light didn't go out and the place was on my way, so I went in. Here's my question: if I hadn't gone to the dealership, would the light have gone out on it's own eventually, or did the error code have to be cleared by the service department? I've had friends tell me that in similar cases the light went out after an hour or so, but none of them drive BMWs. The dealer didn't charge for clearing the code, but why waste their time needlessly? Emanuel
If you leave the gas cap off, the Check Engine light will come on. When you put the gas cap back on, the Check light will eventually go out -- it will not go out immediately.
If you put the cap on, and the light comes on anyway, this can mean that the gas cap is defective. There is a one way valve that allows air to come into the system, but prevents fumes from getting out. The Check light means that fumes might be escaping into the atmosphere.
Your car uses On Board Diagnostics, Level 2 (OBD II), and you can buy the code reader for about what it can cost to have the codes pulled once. There are several levels of code reader, witht he more expensive units having more features. I've found that the mid-range models costing about $100 (USD) -- available on eBay, or your local parts store -- have the features tha tmost of us need to work on our own cars and trucks. You found a benevolent dealership employee that reset your codes for free, but there are ample stories of this service costing in the range of $80, and troubleshooting services running to several hundred dollars.
There are also auto parts stores that keep a couple of the code readers on hand for customers to use for free. You drop your driver license and carry the reader to the parking lot to extract the codes and reset the circuit. Or, you can buy the reader on a credit card, then get full credit when you return the reader, this strategy lets you take the reader home for the weekend if you think you need to do more trouble shooting, or replace a few parts. Basically, you get to use the reader for free if you bring it back when you are done using it.
I would advise you to not worry what is wrong, and watch for the light to come on again. Then get the code and keep a record and reset the light. THEN, the next time the light comes on, compare the code with the record you are keeping, and if the same you have something to fix, if different then you either fix something or keep another record. The codes in the range of P0440 to P0459 indicate problems (mostly leaks) in the Evaporative Emissions Control System -- which will point to the gas cap or breaks in hoses. (Since your car is reasonably new, I'd discount broken hoses.)
I've heard about code readers but have no direct experience since these are my first cars less than 20 years old. Where do you find listings of what all the codes mean? I'm betting they vary by car manufacturer. Emanuel
That's the beauty of the system, Emmanuel, they don't vary all that much.
They came out with On Board Diagnostics (OBD I) back in the mid- to late '80s, and found that consumers were getting screwed because the codes and the equipment needed to extract them were not standardized. You would take your car to the mechanic and I'd take mine, and the mechanic would have to keep at least two different tools to extract codes. The tool costs $1500, so some mechanics would not buy them and as a result they spent lots of your time and money chasing the new technology looking for stuff that had nothing to do with the problem. The more cars the mechanic "claimed" to service, the more tools he had to buy or work without. If he bought the tools, then he sold them back to you on a per call basis, typically at a rate of about $70 - give or take. If he worked without the tool, then he would replace the wrong stuff, costing you about $70 - give or take.
In 1996, all cars and trucks sold in the USA were required to comply with OBD II. This standardized the location of the data port and the convention of the data stream. The data port is located along the bottom of the dash board, generally in the area to the left of the steering wheel. I've seen some that were right under the steering column, but most are along the bottom edge where the clutch pedal would be if there was a clutch pedal. If you look along the bottom of the dashboard where your left leg rests, you will find the data port. The specification requires it to be exposed and easily accessable, but I've seen hidden data ports behind a fuse cover, with markings on the cover that CLEARLY indicate that the data port is hiding there. (How hard could the port be hiding if there are markings that clearly show its existance?)
The data port is easy to find, and they are all the same, so the OBD II tool will fit any '96 or later car or truck. There are a few unique codes, but any system that can produce a code will produce the same code on all systems that can make it. For example, if there is a Framis Valve, then all cars that have a Framis Valve will produce the same code to indicate that Framis Valve needs attention. If the car hasn't got a Framis Valve, then it will never display the Framis Valve code. There are a few codes - a very few - that Chrysler or Ford will produce that other cars will not produce, so there is a minor exception to the afore mentioned rule.
Go onto eBay and do a search for OBD II, and there will be several scan tools that come up. One of the manufacturers (AcuTech, AcuTron -- some mind of name like that) makes 4 different tools, the cheapest being about $60, the most expensive running in the range of about $200. There are two models that straddle the $100 price point, I'd recommend either of these for your home tool kit. I'd actually recommend visiting the local auto parts stores to see if any will loan the tool to you, my local AutoZone chain will do this. If you want the convenience of having your own, then buy one that is on either side of the $100 price point. These will give you the code and a text message of the meaning, and let you reset the codes that are displayed.
Once you have the reader, use your favorite search engine and search for "OBD II", this will return a list of Websites that explain OBD II in detail, and many have the codes listed for you.
There are manufacturer-specific OBD-II codes, however. IIRC, the latest Bentley BMW manual (3-series, at least) lists codes and their meanings. You can also look up some online at:
I bought the car Saturday, so seeing the check engine light after 3 days of ownership was a bit more nerve-wracking. :) I had my heart in my throat the entire 2-mile drive to the dealer. Driving it around with it on for 2 days would've killed me. Emanuel
I felt the same way until I found out that the gas cap (or a related sensor) was the momentary problem and that the "check gas cap" warning light" described in the manual doesn't seem to function. (I'm happy to report that the fuel reserve icon next to it does light when you have about 2 gals. left.)
Another odd thing that happened to my Z4 (also a 2003 3.0) was that the oil level warning light came on intermittently at about 7,000 miles. I checked it on level ground and was only down a bit more than 1/4 liter, but I topped it off anyway. I do change oil once between each scheduled service, and have never seen the warning light since the first change at 8,000 miles.
I can sympathize with you and think it is entirely retarded to set off the "Check engine" light for an entirely emissions related faults such as this. Does anyone believe the engineers did not know that leaving the gas cap off was going to send owners running to their dealerships?
The OBD II code reader should be able to read all of the codes. If BMW has codes that nobody else has, then so what if the code reader can display them?
I haven't got a E46, but I wouldn't hesitate to go down to the corner and use the code reader for free to see if I could figure out what was wrong iwth my car. And, if the gas cap was the problem, the reader would tell me. It might not tell me a unique code, but I can't imagine why the contents of the computer can't be puked out and displayed. The reader doesn't really "know" anything, it just displays what comes down the wire, and by default, only faults come down the wire so the code reader should be able to keep up.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.