first of all - thank you for the valuable forum. I've been developing some OBD related software, and it has been really helpful :)
My question is this - assuming I have an ELM327 chip, and assuming that I somehow obtain all the proprietary PIDs and codes available - is my ELM327 as capable as any other scan tool?
Will I (with the correct knowledge of codes etc., which I know is tough/expensive) will be able to access all the car's information using a simple ELM327 chip and connection?
In a word yes.... More expensive solutions may be a little more stable but otherwise are faster and have better buffering capability. At worst you could drop some data if you don't retrieve it fast enough is my impression. But compatibility wise they should all work pretty much the same assuming it is compatible with your cars ODBII protocal which it should be.
All the car's information? NO.
A lot of makes use different pins for different systems.
Without modification the ELM327 is not capable of communicating on those different pins.
Never mind the fact that an ABS or an Airbag could use an entirely different protocol which the ELM327 cannot support.
What are you talking about? Your statements go against the experience of a majority of people that have played with the ODBII interface.
ODBII started out with many different hardware "standards" but recently has settled on CAN and all currently made cars sold in the US have to use this standardized ODBII bus. The ELM327 and compatible devices can connect to any of those older standards as well as the newer standard. The whole point is to be able to connect to your vehicle and talk to it in a very simplified matter. I have no clue what p2psmurf is talking about. Everything in your car is tied to either the high speed or low speed bus and as far as I know they are accessible through your ELM327 device because they are on the ODBII bus. And anything that might not be connected directly to the ODBII bus is likely connected to your BCM or Body Control Module.
Fortunately the data that is transmitted over ODBII is pretty standard. You can do a search and find out the structure for the commands and data sent over the databus. As the standard has developed you have been able to get more and more standardized information as well such as vehicle speed, engine temp, o2 sensors, trouble codes. However room was left for proprietary codes to be used which is where most of your manufacturers have made it difficult. You can definitely connect to your ABS and Airbag modules which is why you have to be careful when you are messing around. The information is apparently available but as mentioned elsewhere is very expensive and hard to obtain unless you just happen to have a buddy that works at an aftermarket manufacturer that had access to the information.
When you do this you will benefit from having a shop manual for your vehicle. The one that the dealer uses. I was looking through mine for my GM truck and it told me what the module names are, what they are used for and their PID's which helps make things a whole lot easier to track down. If you do your homework and research what modules you want to interface into it is likely you can find the information you want but it won't be easy to do.
OBD2 only applies for emission related ecu's, i.e the engine and the transmission.
Anything else is entirely up to the manufacturer. If they want to use smoke signals to talk to an ABS that's allowed.
Never mind the fact that a lot of vehicles have more than one can-bus (up to 4 now), which in a lot of cases cannot be accessed from the standard pins from OBD2, they are located on other pins.
So. how would you connect to the ABS in a Fiat which is located on pin 1 and uses a proprietary protocol?
Just don't do it on some Fiat models that are re-badged Peugeot's and have a permanent 12 volt feed on pin 1.
Not everything can be found on the Can-bus. Just the emission related stuff.
And even that is incomplete. For instance, you may find the actual fuel rail pressure, but not the requested pressure.
There are a lot of things not covered by the OBD2 standards.
Things like service interval reset, actuator tests, Diesel Particulate Filter emergency regeneration, etc., etc.
PS: I don't have to search for the structure of the commands and data used in OBD2.
I have all the necessary SAE documents as I write scanner software for a living.
Your information is still very misleading.
The ODBII bus does indeed have access to many non emission related stuff.
As I mentioned, some items you may have to go through other modules to gain the information and such but the newest cars sold in America are required to use the CAN network which is available through the ODBII connector directly or through "house keeping" modules such as the BCM. In reference to GM vehicles at least everything is available through the ODBII connector. A mechanic with a dealer tech tool can access every module in the system through the ODBII port. They can access and reprogram just about any module in my vehicle. The Windows have nothing to do with emissions nor do the lights or seat position but these can all be accessed through the ODBII port. If I want my cluster reprogrammed or my seat switches or my seat control module reprogrammed they go through the ODBII connector.
As I understand it both Ford and Chrysler do the same. But the older the vehicle goes back the less that is tied into the CAN or ODBII bus.
There are examples on this board of MANY users accessing MANY features on their vehicles through the ODBII port. It is NOT just for emissions. The standards in place have standards for many of the basic emission items but as I said before, anything beyond the basic are driven by the manufacturer. Also as I mentioned it shows in my shop manual the PID to access the modules in my truck. I can access pretty much everything in my truck from a tail light to a flasher from the ODBII bus. Of course I need to know what the actual command is to do that which the manual does not provide but I did see a table where the PIDs were listed.
You have the SAE documentation but do you have the OEM specific documentation that goes into those details? Because as I stated in this and previous message. Your posts do not match the experience of other members who have used ODBII sniffers and figured out many of the unpublished codes to control many aspects of their vehicles. The information you have likely only relates to the specific items that are defined by the standards put in place and do not relate to other specific items as related by the manufacturers. The emission codes and such are easy to get. Its the proprietary codes that deal with other devices that are difficult. You can still "sniff" many of the codes by monitoring the databus and using the item you want to track down. Such as a window going up or down.
If you don't believe me watch this or a similar video.. It is eye opening and they are accessing everything solely through the ODBII port:
(Scary part is the vehicles with blue tooth will open the ODBII bus wirelessly to the world once the security is broken.)
Also follow the related article where they talk more about this.
Not sure why they tore the dash apart because the article talks about them connecting to the entire network through the ODBII port.
I should add a disclaimer that I only know about my vehicle directly and some outside of that. Makers of cars from other manufacturers may do things in other ways. And the more new your vehicle is the more likely it can all be accessed through a generic ODBII port. But I am sure there are exceptions out there.
First of all, there are more makes than just GM and Ford, even within the US.
And yes, I do have access to OEM documentation for some makes.
One of those makes is VW/Audi and you will not get anything from any ecu other than the engine or gearbox using OBD2 protocols. That goes for both the older ISO protocols and for CAN.
So, without knowing which vehicle the original question relates to, the question cannot be answered completely.
I'm with p2psmurf. and anybody that has anything differently to say just needs to post up how much they spent at a shop to have codes pulled out of the airbag controller, or the electronic suspension controller, or the body controller, or the abs / traction controller, or any other module that is not pcm/tcm while that elm327 sat in the glovebox.