There is a BUS in my MINI
Posted by murmini Thu, 02 Nov 2006 21:23:00 GMT
Traditionally, for every electrical device in a car, the manufacturer ran a wire from a power source, via a fuse and then a switch, to the device and then to ground. When you turned the switch on and the device was energized. With the complexity of the modern car, the system soon became fraught with the possibility of failure. Advances in the computer industry have brought new technology to the automobile engineer and we are seeing more addressable network-based systems than ever before.
The electrical systems in the MINI are connected via a vehicle-specific wiring harness relative to the options that were factory installed. In addition there is a wiring harness within each door and a dashboard harness, again subject to the specified factory options. That describes the physical wiring within the car, but of a much more complex nature is the signal-specific connectivity that manages a host of systems and operations. These various signals travel over wires within the wiring harness and are digital in nature. They 'carry' information back and forth between sensors and devices and assist in much of the running of the car's systems, frequently unbeknown to the driver. These signal paths are know as 'buses' - a term from the computer industry that refers to data paths that connect the various parts of the computer together. Every bus carries signals or messages that consists of 'data,' 'control' and 'address' parts. When a command is sent out along a bus, the other devices ignore it as it is not addressed to them, however, when the data package arrives at the specified device, it does as it is commanded. The bus can also handle two way information so the remote device is capable of sending information back to the controller.
The MINI has a number of interconnecting bus systems: the K-bus, I-bus, CAN-bus, D-bus and the DS2-bus:
The K-Bus (from its German name Karosserie - meaning body) is the bus that permits messaging between various parts of the car and is what they call 'event driven'. Different things are given different priority on this bus, meaning some messages are given preferential treatment over others. The K-bus is a single white/red/yellow wire, and is a fairly slow bus - running at only a few kilobits per second and connects such items as the sun roof module, rains sensor (for rain sensing wipers where fitted), wiper interval control, headlight aiming controls (for Xenons), multi-function steering wheel, electronic drive-away protection (key and security systems), run flat monitor, multiple restraint system and the general (body control) module. The climate control also uses this bus along with other lighting and general body function items. These items can 'chat' back and forth with the general module using this bus, with obvious priority being given to items involving safety over say the entertainment system. The general module also communicates with the instrument cluster to pass information to the driver. This general module has the highest priority on this bus and its messages 'outrank' any others. All devices on this bus receive all the messages but as each message has an address header, they only respond to commands sent to them. This bus is designed as a 'tree structure' with each module having its own branch. This is so that a failed module on the bus, will not prevent a message getting to another module.
The I-bus is a subset or secondary K-bus and connects such devices as park distance controller, radio, CD player, digital signal processor and navigation system to the General Body Module. These buses comply with an international standard called ISO 9141 so that third party manufactures providing many parts to many OEMs can interchange parts.
The D-bus and the DS2-bus are serial diagnostic buses that allow both internal and external diagnostics to take place. The D-bus allows emission-related components to communicate with the on board diagnostic systems. These include the engine management module (ECU) the hydraulic power steering system and the ABS (anti-skid brakes), DSC and ASC (stability) systems. The DS2-bus connect non-emission related modules such as the steering angle sensor and the instrument cluster and subsequently allow data to be passed back and forth with the K-bus. Both of these diagnostic buses are connected to the OBDII diagnostic connector in the drivers foot well and allow the service department at your MINI dealership to look into the inner workings and see error and fault codes. Actually, the OBD is established as an ISO 9141 standard thus allowing repair shop diagnostic equipment to be useful across multiple manufacturer's vehicles. This bus also carries diagnostic information that it can share with other buses.
The CAN or Controller Area Network bus, is the fastest data speed bus in the vehicle and manages such things as engine management, ASC and DSC stability control systems and, where applicable, the automatic transmission. It is a serial data bus and employs twisted pair wires, yellow/black and yellow/brown. The high-speed nature of this demands specific wiring requirements, with termination requirements at both the ECU and the instrument cluster and no spur exceeding 1 meter. The use of twisted pair is very important to eliminate electromagnetic interference. It runs directly between the instrument cluster and the engine control module with three shorter network 'spurs' running off it to the steering sensor, the ABS/ASC/DSC module and if present, the automatic transmission control module. The CAN bus is a very versatile serial data bus system with multi-master capabilities, that is, all CAN nodes are able to transmit data and several CAN nodes can request the bus simultaneously. This is a fault-tolerant network and must work flawlessly in a very hostile electrical environment. The CAN vehicle bus used on the MINI was developed by BOSCH and is a remarkable piece of network engineering.
So there you have it... not one but five buses in the MINI. Of course, much of the MINI bus technology comes with the heritage of BMW and the E-46 3-series models 1999 - 2005. Another reason to appreciate just what BMW brings to the MINI.
I really like these little pieces you put up Murray – it’s nice search material for those that want to know loads about the MINI :)
One of these days you will get me to be as smart as Chad! Maybe I should be a tech . . .
Hiya, I left my mini outside my house, came back later and the convertible roof was half down along with the windows… i don’t suppose you have any idea what could have caused this do you?
Jen – A couple of things: Is your MINI programmed to open the windows and sunroof from the key? To find out, press the remote unlock button and hold for 5 sec – if so, there is a possibility that you have actually activated the remote by mistake and opened them. If you chose to, you can take it to the dealer to have that option turned off. If it is truly happenng randomly, then you may have to get your dealer to replace your General Module.
The car alarm on my 54 Mini has just started going off intermittently. It spent yesterday at my local BMW Mini main dealer undergoing diagnostic tests and they found nothing wrong. At 5am this morning, to my consternation (and that of the family and neighbours), off it went again. The garage said that if this happens again then maybe there is a wiring or management control problem and possibly an expensive remedy. Any thoughts?
Christopher, the complexities of the multiple inputs from the alarm sensing components such as tilt control, tailgate, door and ultrasonic sensors make this a tough one to find. The BC-1 General Module does manage the DWA Alarm system so it may even involve changing out the General Module, which is an expensive option. I am sorry that I can not be of any more help to you.
Is there anyway to recode a key from one MC (2004) to another or is there anywhere I can go to get hold of a wiring diagram. Was given spare uncut (remote) key and want to try and code it as my second key. Thanks heaps for any help. RR
would just like to ask where can i find this evaporative emission system purge circuit valve?my obd resetter says that it’s open..thanks…
Not sure which model MINI you have, but it sounds like the canister purge valve or fuel system is not meeting the spec. When the fuel system is sealed a threshold is checked for a leak. The purge valve is opened and a reed switch is set as the vacuum level is reached. This switch then causes the LDP to pressurize by performing one pump stroke. If the canister purge valve is not blocked in any way, the pulse interval or cycle becomes shorter. If the canister valve is blocked or the tube pinched in any way, the pulse interval remains long, triggering an event alarm. This then tells the ECU and throws an error code. I would talk to your dealer, then see about having the system tested and maybe the canister replaced.
I have been having my SES light come on at random with code P0442 small leak. I have checked hoses, changed gas cap, replaced fuel tank vent valve a front of engine. Now I am in the process of checking wiring from ecu to canister for voltage drops. Can you suggest anything as I going nuts. Ron
Hmm thats a tough one! Sounds like you have the approach down and it may very well be a perished hose. Maybe Chad can ship in with some ideas.
You can have anything in that system cause a small leak….Canister, purge valve not sealing, Gas cap, pump and or o-rings. A smoke test of the system is what I would do to try an pinpoint the leak. Sometimes the leaks are so small that it is near impossible to find and swapping out known good parts are a last resource. I have the advantage of having a GT1 on-site and can retest the system after each attempt. I know that you said that you have checked the hoses, but can you simply block them off, and recheck the system. Do you have the equipment to get the system to self-activate, or are you letting the OBD to do the test after driving cycles? One other question would be, have you had any repairs to your fuel system lately? Putting in a fuel pump or sending unit and not getting the sealing ring seated properly can cause the same thing(ask me how I know!LOL).
HTH,
Chad
Thank you Chad – I knew you would have some good advice on this.
Are all the convenience features (i.e. window roll down/conv.top down) that the dealer activates when requested coded through the factory installed stereo in the Mini? I installed an aftermarket audio system in my 07 Conv. S and when I requested to have the window/top roll down activated I was told it was not possible by the service department because the factory stereo how it is set up. It just seemed strange to me… Thanks in advance…
If it is an R 52 (1st generation convertible) the convenience programming is handled rough the OBD connector and talks to the General Module and would not in nay way be impacted by an aftermarket radio installation. Your dealer may have misunderstood and though that you were referring to an R 56 S (non-convertible) with the new center stack radio in which case they would have been correct.
Do you know what P0136 means with gt-1 diagnostics
Hi Guys, my turn signal doesnt show on the instrument panel,no a/c radio showing,disable.Is there something I can do?
John: P0136 is indicating that your Oxygen sensor (Bank 1 Sensor 2) is throwing an error code and probably should be replaced.
Andrew: Sounds like something more complex is awry that will probably require connection to diagnostic equipment. You can also check if any fuses are out here.