[rRadler]

Within the next days I will visit and most probably purchase a used E91 325i from 2007 with 180.000 miles. In general it has been well taken care of and the maintenance properly registered on the book, but the owner has mentioned to me that it presents only one failure; recently the speedometer and odometer started malfunctioning. He took the car to the closest dealer and they replaced the ABS sensor. This did not solve the problem, and so the mechanic suggested that the problem might be caused by a bad connection of the cable which takes the speed information to the dashboard.

Some time ago at home we had a similar issue with a VW T4. Thankfully I had all the wiring diagrams and, after checking that the ABS sensors worked properly, I took the dashboard out and found out that the speed sensor cable entering the dashboard was kind of broken. I can assume that in the E91 taking out the dashboard is not an easy operation, so before doing so I need to be sure about which cable is responsible for the speed info and how does it looks like (color?).

Additionally, I remember reading that these models also store mileage information on the key. In that sense I am afraid that in the future the mileage on the dashboard and key could differ and cause me trouble with the insurance company (I live in Germany and yearly mileage is a factor of the insurance cost).

My questions are the following:

- Do you know which wire is responsible for speedometer and odometer?
- Do you think the problem could be caused by any other reason?
- Could mileage end up being different at the dashboard and at the key?

PD: I know there are some web pages with WDS for BMW, but I can not make them work in my laptops, both with Linux and Windows. I have also installed a WDS App but somehow diagrams are not being shown. I would appreciate if you know of a place where to download the wiring diagrams for the E9X in PDF format.

Thanks in advance.

[smass]

Wiring diagrams and other good info are here https://www.newtis.info/tisv2/a/en/

There won't be any independent wires for the speed signaling. Nearly all E9x information is communicated on some form of network bus.

[rRadler]

Originally Posted by smass

Wiring diagrams and other good info are here https://www.newtis.info/tisv2/a/en/

There won't be any independent wires for the speed signaling. Nearly all E9x information is communicated on some form of network bus.

Thanks a lot for the link.

In that case I can not understand why only the speed reading is malfunctioning. Shall I replace the complete corresponding control unit?

[lowrydr310]

If you hook up a basic OBD-II scanner/reader it will show mileage and vehicle speed in real time. I did this to verify mileage on and e39 5er that had the mileage display pixelated and unreadable.

Mileage isn't stored on the key, however it is stored in several different modules throughout the vehicle. If that gets modified on any of the modules, you'll see what looks like a little ball next to the mileage on the dash called the tamper dot. As long as that dot isn't there you should generally be safe

If you can get the speed reading from a plug-in diagnostics tool, it may just be the gauge cluster that's broken. Search around the forums here, you can buy a new one and there are apparently a handful of people who can help reporgram used ones.

[smass]

Originally Posted by rRadler

Thanks a lot for the link.

In that case I can not understand why only the speed reading is malfunctioning. Shall I replace the complete corresponding control unit?

It is never a simple parts swap with a BMW. Many control units need to be programmed for your car to work properly. Find a good mechanic who understands this.

[rRadler]

I do have an OBD-II scanner (Carly). I will try that.

Had never heard of that tamper dot. Interesting.

[outkast123]

Is the issue intermittent? (e.g. sometimes the speedo works normally and other times it's malfunctioning?)

I had an issue with the RDC module (that controls the TPMS sensors) that presented with similar issues. It was making everything on the bus go haywire.