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-   -   TechSpec® : Understanding On-Board Diagnostics, also known as ECU, ECM, EMS (https://www.team-bhp.com/forum/technical-stuff/42229-techspec-understanding-board-diagnostics-also-known-ecu-ecm-ems-2.html)

Thanks for the appreciation guys, it does help :)

A lot of reading, a lot of patience and a lot of hair tearing ;) + a thought process on how to keep it simple, straight.
Agree, OBD was developed for emmision monitoring but is now used by many tuners through the OBD port for tuning the ECU's. And the scantools are not the only tools used for decoding and tuning.

Again Agree that the best way to reflash is using the manufacturer scantool but that will reset it to factory settings but the manufacturer tools are not equipped for hardcore tuning like changing the maps etc, they just allow for some very generic adjustments. This does not solve the purpose of professional tuners.

The term "mislead" used by me meant that the original ECU still thinks that its communicating directly with the engine whereas its not for all its other parameters.

@ dadu - That is a plethora of info. will need you help to understand it in detail. But lead me read it completely first. Thanx a tonne for working so hard on it and sharing it with us.clap:clap:

Oh dadu thats a treasure load fo information , thank you very much for sharing

It took me quite a while to get thorugh all that information

Just can't seem to get enough of this threat.... oops! I mean thread lol:. Goin to rate it a 5er

Cheers!
M2S

Thanks dadu!!!

And another five-star from me :)

Good one Mate.

Me being hard core Auto-electronics freak really enjoyed this article.

Any website or a book where we can study deeper into these systems.

Little bit off topic :OT

"Fuel Level Sensor : Reports the output voltage of the fuel level sensor"

Any idea how I can get more info on these. I am interested in information like, is it current based or voltage based, how much current or voltage variation will a car has for a liter of petrol change in fuel tank.

I was trying to build a micro controller based digital fuel gauge for Carb Zen. Tried pouring petrol liter by liter to fuel tank and reading the output voltage at the wire which gives to analog fuel gauge indicator. But it showed constant voltage even after pouring 5 liters of petrol. Did some googling but not much help :-(


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Thanking You for your anticipated co-operation.

Well my bad, the factory scan tools are no longer used only for scanning they are now known as Tech tools and they can have additional plugins to the help them tune or completely change base maps but they still cannot do much with the adaptive learn systems that is where the piggy-back systems come in and do the mis-leading bit. Out of personal experince have done a lot of base map changes on GM cars using the GM TECH III tech tool with additional plugin supplied only to manufacturer dealers by the manufacturer and it is usually when a re-call or tsb is issued, that such a procedure is carried out.
I am not trying to say your wrong but just updating on the right tune conditions or the latest manufacturer play toys.

Nicely done. A wonderfully simple write-up that totals most functions of the ECU setup.

Good work, dadu....

Thats the key, the base scanners are good enough only for the generic diagnostic and I am not even sure how many technicians are even trained enough here, to carry out those remaps using the plugin.

PM'ed you some info, on where to get this.

Ok as far as India is concerned Maruti, Honda, Toyota, GM, Merc ,BMW, Ford have training sessions for the master techs in the dealerships if such a procedure is required as being a mech comes from the family and not through a trade school, but yes most master techs in the big dealerships of most companies do now how to use the tech tools.
As far as I know the GM(parts and service), Formen and lead techs of the one of the RNS group get videos sent to them demonstration on how to use these tools or new toys before the recall or tsb is actually sent out, Have been there and seen it, even have all the info related to the 07 Maruti SX4.
Well just adding more info not contradicting you as I go to a trade school, I am also hold ASE master tech certification. And this is the field that I really love working in.

Thanks for this informative thread Dadu. Need some help from you.

I have Alto LXi that I bought this year. Would you know if it is feasible to to procure OBD scantool for this car.

What I am planning to do:

1. READ ONLY -- No changes to tuning or anything else
2. Hook up Cell phone or Laptop to OBD port
3. Display Engine RPM and other stats on Cell or Laptop.

Have seen Scan tools on net that can transmit data to Bluetooth. Would be ideal if something similar can work with Alto.

Unfortunately as tested by Absar the OBDII compliant scantools dont work with any Maruti cars, therefore its best to peep-in on what scantool the MASS uses and then buy the same.

The Japs are using different standard (ref my 1st post).

Thanks Memo45 for your inputs.

Maruti has just up to a different data streaming also known as the Communication Area Network (CAN) for the 07 model year cars - for which presently they have upgraded fron the Tech-2 to the SDT OBDII interphaser (If i am right it supports all fetures of the Tech-2). Because the CAN communcations speed is higher the aftermarket display and generic scantools do on recognize the OBDII protocol. CAN is also being used in Ford, GM and most European and Japanese cars.

Thanks for the answer Dadu and Memo45

Another noob question..

If I got it right, Maruti uses CAN protocol for OBD. And readers that support CAN should be able to read data from OBD port in Alto.

Is that reasonable interpretation?

Check with Absar or Eapen if scangauge has CAN protocol, if it has, answer is NO, since it didnt work with Maruti cars,