# The TPU garage



## imperialreign (Nov 29, 2008)

Seeing as how many mechanics and hobbist grease monkeys we've got floating around the board, we need a place for automotive discussions - whether you're thinking of getting another ride and want some suggestions; wondering if that local mechanic might be ripping you off; wondering what that strange noise might be; talking street rods, hot rods, or other performance beasts - or just to drool over some new concepts and models coming out . . .

so - hunker down to the smell of burnt oil and wheel bearing grease, new rubber and solvents, and the noise of pneumatic tools!


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## FR@NK (Nov 29, 2008)

I ordered this direct from Germany:

Here is an interface that connects my car's network to a computer via USB connection.


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## imperialreign (Nov 29, 2008)

what kinda car do you have?  Obviously something newer with a CAN system . . . right?


I wish I had the money for a good field laptop, our current scanners can't keep up with the BUS speeds in newer cars . . .


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## DrPepper (Nov 29, 2008)

I am loving this thread already  If I could get any car it would be an old mercedes like the one's ya see driving about in africa since they are dead cheap and reliable.


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## imperialreign (Nov 29, 2008)

DrPepper said:


> I am loving this thread already  If I could get any car it would be an old mercedes like the one's ya see driving about in africa since they are dead cheap and reliable.




I've never been big on Mercs, but those older ones can get quite expensive . . . depending on their condition.


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## 3870x2 (Nov 29, 2008)

there is a club set up in the clubhouse, if its still up, for motorheads.


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## DrPepper (Nov 29, 2008)

Since I don't have a car I'm going to babble on about the shelby gt500  damn that car is awesome


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## KBD (Nov 29, 2008)

a car network????? what the hell is that? You must forgive, i dont know jack about cars and i had no idea they had car networks


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## Kursah (Nov 29, 2008)

KBD said:


> a car network????? what the hell is that? You must forgive, i dont know jack about cars and i had no idea they had car networks



It's a simple serial network so that modules and sensors can communicate. GM has used the CAN for years but it was nowhere near the first company to do so. As a GM Dealer Technician I deal with CAN all the time. I really gotta say that technology has come a long ways, but not all of it is for the better.


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## imperialreign (Nov 29, 2008)

3870x2 said:


> there is a club set up in the clubhouse, if its still up, for motorheads.



well - I was thinking a bit more than just a bunch of gearheads hanging around yakkin . . . something where other non-mechanically inclined users can post up questions and whatnot for us to answer when they're having problems . . . think of it as a partial auto tech-support 



KBD said:


> a car network????? what the hell is that? You must forgive, i dont know jack about cars and i had no idea they had car networks




yeah, the computers in newer cars are networked.  They started doing that around the year 2000 or so . . . it was meant to help reduce the amount of wiring used with a vehicle (if you haven't noticed, there are a ton of wires for each individual system . . .).  But, there will be typically one or two thick wires, typically colored purple, that exists as a BUS system between the individual modules for communication, allowing each computer to share sensory information without having to be directly be wired to each sensor.

They do this with BUS updates - the modules are programmed in such a way that information is synched between them, allowing one wire to be used for these information swaps . . . one module will be programmed to request information about a certain sensor at certain intervals, it's companion module is programmed to send that information at those same intervals.  Very complex, and easy to break down.

Newer systems use a CAN diagnostic system, which is the next thing to replace OBDII - these systems eliminate more wiring, lot's of relays and have one module to controls one system (e.g. one module per door window, door lock, etc).  The sizes of the computers are drastically reduced, and function as the actuator, relay, switch, etc  

Think of a CAN system like a LAN - each module has a specific address, and when a switch is pressed within the car, a command is sent to a main control module (PCM or BCM), which then sends a command to the specific module that needs to be activated, that module then carries out the command.  For example, if you take the LF window module out of the door, and move it to the RR, then press the LF window switch, the RR window will activate.  Although the module has been moved, the address hasn't.

Big problems with these systems, though - if a module dies and needs to be repalaced, it needs to be programmed in to the system.  Also, many diagnostic scanners can't keep up with the speeds these systems work at, requiring a new scanner (which aren't cheap), or a laptop with the necessary equipment to interface with it.


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## KBD (Nov 29, 2008)

Kursah said:


> It's a simple serial network so that modules and sensors can communicate. GM has used the CAN for years but it was nowhere near the first company to do so. As a GM Dealer Technician I deal with CAN all the time. I really gotta say that technology has come a long ways, but not all of it is for the better.



i see, that explains it, thnx!

and imperialreign for his explaination also.


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## FR@NK (Nov 29, 2008)

imperialreign said:


> what kinda car do you have?  Obviously something newer with a CAN system . . . right?



Yea its an older BMW. The main systems (engine/transmission/ABS) use a high speed CAN bus to communicate. The bandwidth on this bus is 60000 packets per second. A slower bus is used on systems like the radio and climate control. The interface above connects to this slower bus. There is a main hub, the speedometer cluster, that connects all the buses together to relay packets from systems on different buses. I hope to use the USB interface to read all the packets and hopefully get an idea of what all goes on within the car's network.



DrPepper said:


> I am loving this thread already  If I could get any car it would be an old mercedes like the one's ya see driving about in africa since they are dead cheap and reliable.


like this?


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## imperialreign (Nov 29, 2008)

FR@NK said:


> Yea its an older BMW. The main systems (engine/transmission/ABS) use a high speed CAN bus to communicate. The bandwidth on this bus is 60000 packets per second. A slower bus is used on systems like the radio and climate control. The interface above connects to this slower bus. There is a main hub, the speedometer cluster, that connects all the buses together to relay packets from systems on different buses. I hope to use the USB interface to read all the packets and hopefully get an idea of what all goes on within the car's network.



I've noticed one issue with the BUS systems on newer cars - the BUS feed itself carries decent voltage . . .

this turns into a problem when some n00b working at a BB or CC or some audio installation joint that doesn't use wiring diagrams for stereo installations . . . I've had a few where our scanner couldn't communicate with the system, and turned out the power feed for the aftermarket radio was spliced into the BUS feed :shadedshu


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## DrPepper (Nov 29, 2008)

FR@NK said:


> Yea its an older BMW. The main systems (engine/transmission/ABS) use a high speed CAN bus to communicate. The bandwidth on this bus is 60000 packets per second. A slower bus is used on systems like the radio and climate control. The interface above connects to this slower bus. There is a main hub, the speedometer cluster, that connects all the buses together to relay packets from systems on different buses. I hope to use the USB interface to read all the packets and hopefully get an idea of what all goes on within the car's network.
> 
> 
> like this?



YESSS


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