BMW E46 K-Bus Devices

Last updated February 12th, 2014

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Every once in a while I get a call from someone who has all sorts of problems with their E46 BMW. Not just door locks, but, turn signals, sunroof, windows, dash lights and the list goes on. I just tell them that it might be a problem with the K-Bus, which usually makes them more confused. Since these problems can have any number of causes I can't help diagnosis it over the phone or through emails. I decided to create a starting point for people to learn a little about the K-Bus. Here is a story of someone who had a K-Bus problems

A diagram which showed everything on the K-Bus.

A1 - General Module
A2 - Instrument Cluster Control Unit
A3 - Light Switching Centre Control Unit
A11 - Heating and A/C Control Unit
A12 - Multiple Restraint System Control Unit
A21 - Driver's Seat Memory Control Unit
A33 - Sunroof Module Control Unit
A81 - Park Distance Control (PDC)
A85 - Tire Pressure Control System Control Unit
A169 - Switch Center
A212 - Mirror Memory Control Unit Driver's Side
A213 - Mirror Memory Control Unit Front Passenger Side
A417 - Tire Defect Indicator Control Unit (RPA)
A836 - Electronic Immobilizer Control Unit
B57 - Rain Sensor
IO1002 - Volute Spring (steering wheel controls)
N9 - Radio Control Unit (head unit)
N22 - CD Changer

The letter number preceding the control unit is the module number. If you want to find it on the WDS just go to control units and look up the letter/number and it will take you right to it. The K-Bus is wire number X10116 and is on a WS/RT/GE (White/Red/Yellow) colored wire with 0.35 diameter or approximately 20 AWG.

The best place to troubleshoot problems with the K-Bus is to first measure the voltage on the bus. It should be +12V or so with occasional low going blips. If the bus is sitting at anything less than 12V then something is stomping on the bus (pulling it low and not releasing it). The way to troubleshoot this is to disconnect each module from the bus and check if the voltage goes back up to +12V. The best place to do this is at the X10116 connector block which is located above the fuses in the glove box. See picture below. All the K-Bus devices come together at this block. The wire to each device can be pulled off individually.

jbeurotech is a mechanic on the E46fanatics forum and has posted many times on the subject of k-bus diagnosis. Here are a few of his posts.

I have my own troubleshooting instructions here. If you find it helpful please consider donating using the link at the top of the page.

GM5 Repair Service web page.

To V23078-C1002-A303 web page.

To V23072-C1061-A303 web page.

BMW General Module III (GM3) Page

BMW General Module IV (GM4) Page

BMW General Module V (GM5) Page