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Discussion Starter #1 (Edited)
I have a 2003 325xi with the common three light plus the speedometer problem. Off and on, I've been working on it. I started out replacing the rear wheel sensors.. With that not providing any help I changed the front ones since it's an all wheel drive. No dice.

However, car has been running rough and I was getting two cylinders misfiring on INPA. It's been 4 years since I replaced the spark plugs and coils I went on ahead and did that figuring it might help. After a misstep of not getting everything connected well enough, the engine function has vastly improved.

On my second trip out though, all of a sudden the miles per gallon gauge started fluctuating and the lights went away and my speedometer came back on. To my knowledge, I haven't touched anything else.

Is anybody have or can link me to a diagram which shows the lines from the sensor to wherever they go then to The Fault lights and speedometer? Is there an isolated diagram?

Also, the odometer quit working. That's problematic if I ever go sell it. Is there any way to get the mileage to read correctly through INPA or what have you? I've seen diagnostic tests which tell the difference. Seems like there ought to be a reset for it
 

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Scan the ABS control module for fault codes. The ABS processes the signal from the wheel speed sensor and then sends the signal to the speedometer and other modules. Symptoms suggest a loose connection somewhere on the CAN data buss.

See: www.newtis.info
 

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Discussion Starter #3
Scan the ABS control module for fault codes. The ABS processes the signal from the wheel speed sensor and then sends the signal to the speedometer and other modules. Symptoms suggest a loose connection somewhere on the CAN data buss.

See: www.newtis.info

Thank you! With my problem having subsided, it went out once again. I think it's a loose connection because I fiddled with the unit, the hood switch next to it and the connections. When I restarted the car that afternoon, it's worked since.

I have seen the url you gave me before, but only looked at it a few minutes ago. Most helpful! I used it to try to figure out how to get my cigarette lighter working again. I changed out the fuse already, but that didn't seem to help. The URL showed that it's a simple circuit. Battery to fuse to cigarette lighter, and it doesn't also have help from any other fuse. The Bentley manual I have is 1258 pages of not much really.
 

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Discussion Starter #4 (Edited)
This might help somebody because so many people have a problem with the brake, ABS & DSC with or without the speedometer working.

After you try to replace the sensors, especially on an xi where any one of them might be the cause, you can stare at the cost of the DSC getting it programmed which can involve learning rheingold and how to set it up and use it Etc.

This actually dovetails with what protocol1 gave me above. After looking at the diagram, it appears to be a dedicated circuit for the cigarette lighter. Huh? Why am I talking about that, right? Simply because the cigarette lighter went out around the same time, doesn't mean that the cause is the same, especially since the two circuits did not appear to have anything related to one another. But wait.

The ultimate issue revealed itself one day when my son and I got in the car to go somewhere. As I was turning the ignition, he plugged in a USB charger into the cigarette lighter car charger plug into the new lighter socket, the three lights came on and then the car died as it was doing back then. Dying on startup was a disa valve issue which was one of the easier fixes. It wasn't uncommon so I didn't think anything of it. I put it in park and turn the ignition..... crickets. Not a light on inside the vehicle anywhere. Completely dead. The battery was only a few months old and it wasn't the issue. However, when I moved some things off the top of the plastic cover over the battery the trunk lights came on. I started up the car. no lights. No other issues. In fact, after I replaced the disa valve, it's run better than it has the entire time I've had it.

Since that time, I've had the three lights come on by themselves and it drove fine like it did for quite a while with them on.

I haven't isolated the exact wire or whether it has anything to do with the small box on the wheel well. All I know is that I give it a tap and it comes back on. And yes, the positive and negative cables are firmly affixed to their terminals.

I have not seen this listed as a possible cause to the three light issues so hopefully this gives someone something to check before replacing that Dynamic stability control module.
 

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Intermittent electrical problems like this are not typically caused by a defective control module. When a control module fails, it will not function correctly, or at all, the symptoms are not intermittent. A loose or broken wiring connection is the most likely cause for the symptoms you described. If you can scan all of the control modules, if there is a fault in the CAN buss between modules, or a power supply problem that would cause a fault code specifically regarding those defects to be stored. Since the control modules communicate with each other via the CAN* buss, if a fault exists between the ABS and the instrument cluster for example, one or the other control module will have a fault code stored. Depending on if a CAN missing error exists on only one control module or several modules can help isolate where the CAN buss fault is located. It is also possible the problem involves the power supply or ground wiring for that module, that would have module power supply fault code stored.

*Controller Area Network, Ref:https://en.wikipedia.org/wiki/CAN_bus
 

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Discussion Starter #6
Thank you protocol1! It didn't seem for weeks to present as intermittent until it the lights went off. It never went in limp mode.

Trying to read the modules has been frustrating. I have INPA installed on my laptop and it will give me fault codes, do live values etc but when it comes to reading the modules, it will detect the presence of about three or four and I get nothing on the rest of them.

I downloaded ISTA and have yet to get it to communicate with the car at all despite switching the port settings back and forth and going through those details. As I write this, I'm reminded that I did get a fiber optic line this week. I could scrap that install of ISTA and it wouldn't take me nearly as long to download it from another link. I appreciate all your help.
 
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