Proper Citroen Obd Diagnostic Tester, Lexia 3

[noz]

The Lexia info is as follows:

Current Version of Diagnostic Tool
V346.33 CD-Rom 46 Pack 10

Communications card identification
APPLI_XS_Fuji_P106138A V4.2.2
@Actia 09.04.09

Communications card software
V4.2.2


The above is verbatim from the info page of the menu.

Cheers

noz

[noz]

Hi Robert,

Whats the Bosch part number on your ecu? It should be in the form 0 281 001 XXX.

cheers
noz

[robertxmb]

Hi Noz,

The Bosch ECU in my 2.5 TD is marked Part No. 0 281 001 589.

Thanks also for the Lexia details.

Regards,

Robert.

[bobhalliday]

Hi Noz.
I'm getting an occasional ABS fault but can't trace it. When I get the fault and test the pins it all reads okay and the fault dissapears for a little while. Both front Sensors are soldered instead of the dodgy plugs and were great for about one month.
I could do with a test with your kit whenever it suits you.
Regards.
Bob.

[noz]

Robert,

I'm compiling a list of ecus with their part numbers and model numbers. It'll be done shortly.

Bob,
You are very welcome. The ABS ecu will have the fault stored so at least it will allow you to target the problem more precisely. Give me a buzz when you want to pop up. Any evening is OK as is Sat pm or Sunday. Let me know.

Cheers

noz

[robertxmb]

Noz.
That's fine, I am away for a week and not in any hurry, I look forward to your results when available.
Regards,

Robert.

[xmexclusive]

Hi Noz

For 2.5 ECU's the Bosch number is not sufficient to identify.
Read off those to hand:-

Bosch No. :Citroen Part No.: Evolution Type. : Eprom No. : ORGA No
0 281 001 212 : 96 157 661 80 : L17 : MSA11.L : 6591
0 281 001 212 : 96 237 486 80 : L18 : MSA11.L : 6820
0 281 001 589 : 96 286 071 80 : L3.17 : MSA11.L3 : ?

Cannot check the active cars for later versions. At least 2 of those are R reg.
Have done a bit of tracking down for the reasons for changes but no idea where the notes are now. From memory there were EPROM changes for the smoke/recycling/cat (3), a single change for the 2x2 to 1x4 glow plug arrangement (ORGA 6800ish) and multiple changes to the immobiliser routines including 2 in 1996. From experience the glow plug change prevents ECU interchange without EPROM swapping. Doubt the smoke changes will be critical while the immobiliser ones depend on which way you go (lose functions or lock up) .

John

This post has been edited by xmexclusive on May 24, 2010 11:35 pm

[Kit]

Hi Noz,

[Kit]

Hi Noz, Bit of a late reply to your earlier post about data sniffing. How far down the road have you got? are these sites of any interest or have you seen them already:

Freediag
InterfaceOBDII

I have written a lot of real time comms code for micros but not for 10 years so I am rapidly getting out of date. Having used VagCom for my VW group cars I find it frustrating that I cannot read the ecu's on my s2 2.1td XM. I have a simple code reader for VWs that just plugs into the standard obdii socket, I hot wired it to each pair of K and L lines in the 30 pin connector and although I got no useful results, it was definitely trying and did reset the ABS Ecu for me. Inside the code reader is the normal interface circuitry and a socketed Atmel micro. To use the jargon, 'it would be a simple but non trivial task' to reprogram the Atmel device and if I knew the protocol it should be able to work with XMs. The other approach I am considering is using a Pic/Atmel device to handle the comms with the ECUs and then use a USB interface back to a PC to act as the Human Interface Device, as I suppose I have to call it these days, it was just an operator console in my day!

How exactly were you sniffing the data, I would have expected that given a buffered interface you would be able to display the data comms on any terminal or terminal emulator. From the printouts I have seen on the web it looks as though the data is ascii encoded hex and each command/ response is terminated with a LF. Tell me I am too optimistic!

As you will realise I know b-gger all about OBDII but would like to learn.

Cheers, Kit

[noz]

Hi Kit,

Sorry, I must have missed your post.

If you know very little about OBD then you are in good company. My knowledge is very limited. I did spend some time trying to reserach it before I bought the chinese cloned Lexia. Now I have the Lexia, the drive and incentive to crack the coding has evaporated. I too considered how to build an emulator using a PIC and the Atmel chip ( cant recall the code right now) but didn't pursue it to completion. What I did learn was that cracking the comms was only the first step. The, arguably, harder step was to build a table of question commands and all the permutations of response. Having the Lexia would help that process because it gives a list of possible responses in the Lexia software which are easy to view.

I took my Lexia to pieces and verified something I'd long thought was true. In a modern car with CAN and VAN all the ecus are 'multiplexed' (the french word for sharing a common bus. Not strictly the true use of the word) or share a common bus (on CANBUS or VANBUS respectively). Therefore you only need two (or four) wires for comms to talk to every ecu. The XMs are pre CAN and VAN and therefore each ecu has its own discrete comms bus. Each of the comms buses on the ecus is wired separately to the 30pin socket under the dash. Now the tricky bit. If each ecu bus is wired to a separate pair of pins and the atmel chip can only be connected to one chip at a time, how do you swap which pair is connected to the Atmel chip? Simple, you just have an array of standard 2-pole relays and for whichever ecu you want to communicate with the respective relay is energised connecting that particular pair to the Atmel chip. By definition it can only talk to one ecu at a time. If you listen closely to the Lexia when you switch between ecus you can hear the respective relay pulling in.

Since the bulk of the work is creating the lookup table for the commands and respective responses, having a working Lexia at your disposal must make the job easier since you can sit for hours sending the same command from the Lexia to the ecu and watching the responses using a serial sniffer. After a time you are bound to be able to work out the codes. Alternatively, if you knew which chip in the Lexia held the codes you could read the chip whilst still on board the pcb.

I still maintain that my ultimate goal, once the command table is built, is to make a mini-Lexia which outputs to the dot matrix display which uses VAN. Then you can display all of the ecus data live on the dash. Particularly interesting would be to show hard and soft mode for the suspension together with the various sensors as a means to fault find one stuck in hard mode all the time.

If you think you might have enough electronics knowledge and consider it possible then I'd be willing to cooperate with some effort in that direction.

Cheers

noz