Controlling Logic?

[whitenemesis]

The more I read about the electronics in my car the more I wonder, "what is the controlling logic? Where is it stored?"

I know there are a number of SAMs (what does SAM stand for?) that control functions depending on certain conditions.

Is there an overall logic ladder somewhere? Are these akin to PLCs? Or is it just hard wired switching?

I know that the wires carry information in digital form, hence the need for STAR to enable functions and let the "system" know what modules have been installed.

Anyone shed any light on this?

 

[Alfie]

You need to speak to Richard again He knows more about all this than anyone I know.

 

[BlackC55]

SAM is Signal and aquisition module.

A SAM will turn on and off components linked to it when it gets the signal to do so from another control unit or switch over the CAN network (Controller Area Ntework)

Alot of the logic goes through a "gateway" of some kind. Most only have one (ignition switch) and some have two. Audio Gateway and normal Gateway. The CAN signals get sent and recieved and the control units decide wheather the signal is for them. There is generally two Can networks that work at different speeds (body and engine). Engine CAN works alot faster due to safety items such as esp needing to work very fast.

The engine and body CAN's communicate through the cars Gateway.

What is a PLCs?

 

[whitenemesis]

SAM is Signal and aquisition module.

A SAM will turn on and off components linked to it when it gets the signal to do so from another control unit or switch over the CAN network (Controller Area Ntework)

Alot of the logic goes through a "gateway" of some kind. Most only have one (ignition switch) and some have two. Audio Gateway and normal Gateway. The CAN signals get sent and recieved and the control units decide wheather the signal is for them. There is generally two Can networks that work at different speeds (body and engine). Engine CAN works alot faster due to safety items such as esp needing to work very fast.

The engine and body CAN's communicate through the cars Gateway.

What is a PLCs?

Thanks for the explaination, Black.

PLC = Programmable Logic Controller, used extensively in automation and control systems.

 

[television]

Thanks for the explaination, Black.

PLC = Programmable Logic Controller, used extensively in automation and control systems.

PLC Pubic limited company, or that is what you need when they go wrong

 

[television]

I am finding you a MB training program that explains it all, I have it just deciding what to do with it

 

[premmington]

If you buy any faultcode reading kit, it must be Can compliant and be able to read the new type 29 bit identifiers (Can 2.0B) as well as the old 11 bit identifiers (Can 2.0A). Even if you don't understand this, it is a question you need to ask when buying diagnostic equipment.

Serial data output (sensor graphing) via the old style K+L-line, or the newer superior Can hi-low terminals of any diagnostic socket, K-line outputs have a data rate of 10400bps where Can2.0A is 500.000bps and Can2.0B is 1.000.000bps. Output that is supplied by the ECU & displayed by Tech2, Bosch KTS , later Snap-on & main dealer spec diagnostic equipment is unreliable & misleading. Apart from adding cabling and test equipment to the circuit in question thus increasing the margin of error. It does not exclude the host vehicle cabling, where over 50% of the faults are situated. Any volt drop or resistance in the host cabling will alter the results, giving the impression a perfectly functioning sensor is at fault. Plus with Can-Lin networks, any data transfer glitch will show as complete network failure. When in fact the definitive but time consuming method is to backprobe both ends of all of the network links between the multiplexers (nodes) with a dual channel oscilloscope, comparing the stored waveforms, subsequently they need to be identical for the system to work. As a matter of info, most people fear Can-Lin bus systems, but in fact they are very simple & reliable. All network inputs/outputs are testable & most faults are caused by glitches which can be traced back to electrical interference (noise) from high output coils, ignition, central locking solenoids etc. etc. Some early systems lacked shielding and had little or no thought put into where the can-bus cables were routed. Higher or lower frequency interference (noise) will be very evident when comparing waveforms recorded on to an oscilloscope. Mildly damp connections cause problems, they don't need to be wet or corroded, just damp! Forget WD40 or duck oil, use compressed air from an airline fitted with water trap to dry connectors.

http://www.remmington.plus.com

 

[whitenemesis]

Thanks for the link & info premmington!