Quote:
Originally Posted by J!m  John, I think you are taking the overly paranoid stance on this.... |
My first and second reactions to this and the rest of your post was: Man, what was that all about???. And then
much less seriously: Fine, but you just stay away from my car!
I think three different issues involving the instrument cluster and EWS-II are getting mixed together here, corresponding to three different functions they perform.
The first is the rolling security code the EWS-II compares against the ignition key to decide if the car may start. BMW, with the EWS, takes a somewhat paranoid stance about how it works and continues to play a cat and mouse game with European car thieves who want to "export" German cars. My post had nothing to do with this, however.
The second issue is the odometer reading kept by the instrument cluster, either internally, or after 1996, in an externally coding plug. BMW, through the manipulation checks and dot you mention, is somewhat paranoid about the stored distance. They continue to play a cat and mouse game, this time with cluster manipulators and car owners, who roll back the odometer for profit. My post also had nothing to do with this.
The third issue is the information that is kept in the instrument cluster about the particulars of the car. BMW decided to call this information the "Zentrale Coderiungschluessel" (ZCS) which they then literally translated to the "central coding key" in their service documents. The "central coding key" is a little long-winded or strange sounding or both for native English speakers, so most just talk about the "central code". While the German original makes good sense, the two translations can be a bit confusing.
To a native speaker, the "central code" and "central coding key" suggest the key to a lock, and that the ZCS locks part or all of the car, and prevents it from operating. While that is one of its functions (in a few slight and particular ways), the ZCS has a much more important function and role for the customer and the dealer.
The E36 3er was produced with many different engines and options, so many in fact, that BMW used to boast that, on average, you would find two identical cars in production perhaps once a day. (Or perhaps half or twice that: I don't remember the exact statistic.) It would have been impractical and too expensive to produce different electronic components for all the different E36s rolling off the line. Instead, BMW designed and installed a much smaller set of common components in all the different cars, and then electronically configured each component to work in the car it is in. For example, BMW put the same OBC in an American 318ti and a UK 323i compact but then electronically configures the U.S. OBC to work with the 4-cylinder engine and display American MPG, and the UK one to work with the 6-cylinder engine and UK gallons.
The ZCS/central coding key/central code is a long string of bits that specifies everything about the car an electronic component might need to know for it (and the car) to function properly. These include the market the car is being built for, crucial particulars about the engine, and all the car's options a component might need to take into account.
Thus, the ZCS really has nothing to do with the car's electronic drive away protection (EWS) other than specifying the particulars the EWS might need to know to function properly. Translating ZCS as the "central coding key" or the "central code" was somewhat unfortunate. Calling it, say, the "electronics configuration string" or the "vehicle particulars" might have been more suggestive.
To recap my earlier post, the E36 instrument cluster is the original and primary keeper of the ZCS / central code. To configure an electronic component you have just installed so that it works properly in the car, you hook up the BMW MoDiC or DIS tester and have it copy the ZCS stored in the cluster to the component. If you skip this "coding" step, the component will suppose it is still in the car it came from. This won't be a problem if that car is similar enough to yours. However, if the donor car is significantly different, the part may have unhelpful notions about your car and not work properly, or not work at all.
The instrument cluster may be the first place you discover something is amiss. Like the other electronic components in the car, it tailors itself to the car according to the information in the ZCS, the information in
its copy of the ZCS, since it is the keeper of the central code. If the cluster came from a car with a different engine, it may incorrectly display the fuel consumption or the engine rpm, for example. I gather, some people can and do live with that.
Having the false code in the cluster, however, may cause problems if you take the car to someone for repair. If they replace an electronic component to eliminate a fault, and then code it, they may fix the original fault but then find that replacing the part makes the car malfunction in some other way(s). If you are lucky and the cluster is also malfunctioning and the tech notices that, he might exclaim "You dingbat, this cluster is a used replacement that hasn't been re-coded!", code the cluster, and then recode the component. If he doesn't noticed, perhaps because the central code is wrong in a way that doesn't disturb the cluster, he may $pend some time in a state of confusion before he recognizes and corrects your sin of ommission.
Let us suppose I have convinced you to recode your salvaged instrument cluster. If the cluster is the keeper of the central code and you have swapped out the original, how will the new cluster get a copy of the old cluster's code? When a dealer swaps a cluster, they start with the old cluster in the car, hook up the DIS tester or MoDiC, read out the cluster's ZCS, install the new cluster and then write the old cluster's ZCS back to the new one. If the old cluster is so broken that the ZCS is unreadable, the tech either reads the code off a label under the rear seat bench and keys it in by hand -- or for later E36s, the MoDiC or DIS tester retrieves and uses a second copy of the ZCS stored in the EWS-II module.
Anyway, this story of the cluster, EWS and the central code seems more like dull book keeping to me than paranoia. It is like deciding how to write a message someone will read in 150 years time. Should I use a pencil or a ball point pen? (I believe the safer answer is a pencil because some inks fade.)
I have got to stop writing such long posts. I hope I have not been belaboring the obvious, and that you guys did not find this treatise uninteresting!