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View Full Version : BDM vs. OBD read on various ECUs



chris_e36_328
21st July, 2012, 12:53 AM
Hi all, I know this is covered in bits here and there, but I would like to make a definitive post as to the real differences between an OBD and BDM read for purposes of performance tuning as well as disabling the DPF.

What started it was a heated debate I had today with owner of one of the garages I do some work for. The type who knows it all you know? The type who got himself a galletto 1260 and mpps, spoke to a few people on some forums, and now brags about how bad my work is. My background is in electronics so I do understand that there might be instances where a BDM is of more use than an OBD read, but as I don?t write files but use variety of tuners, my knowledge is pure theoretical here and does not take into consideration the real differences between various ECUs and real world tuning.

Today I had a pleasure to hear statements like: ?obd read is shit and the dpf cannot be switched off properly, it can only be bypassed, whereas bdm read allows the dpf system to be switched off properly? and ?yes, it is true to all cars?, and ?yes, all dpf removal jobs should be done by BDM?.
I do understand the concept, but claims like this are too bold I think. But when I say it is not true, I don?t really have experience to back my claim up either.

Now, apart from obvious benefits of a BDM read (full backup/recovery, immo/cloning, access to all software and data areas):

1. are there important areas that are not accessible by obd read that are crucial from either performance remapping or dpf delete perspective?
2. if it is applicable only to some ecus, could you state which ecu?s have to be bdm?ed to access useable data, and which ecus will allow for a ?half decent? job, but bdm will make for a nicer tune/more reliable dpf off. And also which ecus are absolutely fine done by obd.

For example: VAG 2.0 tdi 140 bosch, VAG 2.0 tdi 170 siemens, Vauxhall 1.9 cdti bosch

Could those of you who actually have first hand info on the real world differences chip in please? It would help all us installers like myself to deal with idiots like the one I had pleasure to debate today.

cheers
Chris

obd.tech
21st July, 2012, 02:55 PM
Good post/question Chris.......hope you get some good answers.....i'll be keen to learn some answers also

chris_e36_328
21st July, 2012, 03:34 PM
Thansk, I really hope those who make their own files will come through and set the argument straight without need to reveil their own tricks and sollutions. the post will hopefully contribute to those who get to use these files, as there is too much invented and blown out of proportion theories out there distributed by people who really have nothing to do with this field whatsoever.
As said, the problem is that installers have only limited knowledge as to exactly whats going on, so it would be nice to feel like there is a team behind who does supply certain information to make our lives easier.

J_amb_o
21st July, 2012, 10:53 PM
It depends on the ECU. Siemens PPD for example, certain axis data missing from an OBD read.

chris_e36_328
22nd July, 2012, 01:40 AM
So take the PPD for example, does it vary depending on software version as well? I done a fair few with different tuners via obd, but have got one case where the car smokes a fair bit. To me looks like a regen, but there are no corresponding symptoms that would normally accompany it. How about the bosch 140 vag? I have one, again done enough of them to assume obd read is good enough, but now have got a stinky one. No bad smoke, drives ok-ish, no obvious signs of regen taking place, but it smells with unburned diesel inside of the car. if it is the case of this SW needing a bdm read how do we, or tuners know in the future which do require obd and which bdm?


It depends on the ECU. Siemens PPD for example, certain axis data missing from an OBD read.

fes_786
22nd July, 2012, 05:42 AM
i might not be right but here is my thaughts

in the ecu u have 3 memorys

flash
eeprom
cpu

i think with obd read u are just getting the flash memory

with bdm u can read all 3 memory

and as for tricore .etc same principle but have to force / hack security to read

chris_e36_328
22nd July, 2012, 11:38 AM
Yes, youre right mate, tbough cpu is nit aleways there. But this isnt really the case here. The issue here is that the flash read via bdm is complete, whereas flash read via obd does not pull all the data out. Thats the real problem.

ghostridersa
22nd July, 2012, 11:56 AM
I will be watching this post with great interest as I have the same questions as you and would like to hear the feed back from the more experienced members out there.

micromax
22nd July, 2012, 02:52 PM
in edc16 and other ecu with motorola 55x by obd you can read only data map part. not full flash. if you compare flash from bdm and obd you see differents. lenght both files is same, but in obd some first blocks have FF FF FF only. if you read flash by obd, and write to ecu by bdm car don`t start. when i mod maps in ecu i always read full by bdm, then modify and write by obd. i always full backup. only in edc15 flash by obd reading completly.

turner
22nd July, 2012, 03:05 PM
when i mod maps in ecu i always read full by bdm, then modify and write by obd. i always full backup.

Can you please explain why you do it like this?

Thanks

micromax
22nd July, 2012, 03:30 PM
i kill one time edc16 from audi s4.i read and write by byteshooter ori and when i program 3 times ecu death. next i read by bdm , in mpc i see only FF FF FF i search orginal files by 3 months. this is big lesson for future for me.

chris_e36_328
22nd July, 2012, 03:32 PM
in edc16 and other ecu with motorola 55x by obd you can read only data map part. not full flash. if you compare flash from bdm and obd you see differents. lenght both files is same, but in obd some first blocks have FF FF FF only

Agreed mate, but thats common knowledge now. The real question is, whether there is anything important or useable for either performance tuning or dpf delete purposes in the areas that the obd read cannot pull out. And if yes, what ecus is it applicable for.. C39 for example? The fact you prefer to do bdm read every time is really only helping you out when it comes to issues with writing if all thats ever needed for modification is available in the obd read.

chris_e36_328
22nd July, 2012, 03:34 PM
i kill one time edc16 from audi s4.i read and write by byteshooter ori and when i program 3 times ecu death. next i read by bdm , in mpc i see only FF FF FF i search orginal files by 3 months. this is big lesson for future for me.

Isnt the byteshooter a problem here? Now, I dont use one, but good friend of mine keeps slagging the thing off for issues with writing.. Sometimes it takes him 3 of 4 attempts to write a file in he says

danielm
22nd July, 2012, 04:37 PM
hi
Bdm full read.
Write BDM for OBD, with modified areas bdm zone (FF)
The writing?

Best regards

chris_e36_328
22nd July, 2012, 11:45 PM
hi
Bdm full read.
Write BDM for OBD, with modified areas bdm zone (FF)
The writing?
Best regards

what do you mean mate?

gezame
23rd July, 2012, 01:44 AM
in edc16 and other ecu with motorola 55x by obd you can read only data map part. not full flash. if you compare flash from bdm and obd you see differents. lenght both files is same, but in obd some first blocks have FF FF FF only. if you read flash by obd, and write to ecu by bdm car don`t start. when i mod maps in ecu i always read full by bdm, then modify and write by obd. i always full backup. only in edc15 flash by obd reading completly.

Hi
This is not entirely true, depends on the ECU, and the interface is used to read.
There are many EDC16, in which certain interfaces can read the complete file obd flash, exactly the same file I read with bdm.
B.r

chris_e36_328
23rd July, 2012, 10:14 PM
Hi
This is not entirely true, depends on the ECU, and the interface is used to read.
There are many EDC16, in which certain interfaces can read the complete file obd flash, exactly the same file I read with bdm.
B.r

that's the kind of info that's needed here :-)

micromax
5th August, 2012, 12:08 PM
please give an example how the equipment to read and what ecu can read full flash by obd.