Proper Citroen Obd Diagnostic Tester, Lexia 3

[noz]

Hi all,

I recently invested in a Lexia 3 clone from the world of copies, China. This is the diagnostic tool the Citroen garages use to plug into your car for fault finding. With it came the big brown 30 pin plug for the older Citroens i.e. XM's. It also has the standard 16pin OBD plug for any newer PSA car.

It does everything; engine, suspension, abs, air con, mirror, gearbox, heating, pyrotechnic seat belts, air bag, alarm, keypad, central locking, deadlocks and anything else I've forgotten.

For anyone close enough to Falkirk, Scotland you are very welcome to come along and plug the computer into the car to check on any faults, reset fault log or retrieve live data.

Unfortunately the PM messages system is not working at the moment so you'll need to contact me through this post.

Please let me know if this would be of use to anyone.

cheers

noz

[lez]

Is there any engine ecu it wont work on, I know it wont touch a 2.1 s1 diesel, it has no ecu lol, but what about the petrol injection cars?

Its out of my budget if its more than 50p anyway this is an an educational interest, does it have a paper manual, and does it say what flavour of (twisted and abused) obd the s1 v6's use, reason is I'm after building a full LCD dash, so protocols are important to my data sniffing...

[citroenxm]

I got one of these too Noz!

Extreamilly usefull, I plugged it into mates S2 Exclusive TD XM, via the massive socket and when I looked at suspension section, it actually showed the body movment sensor working, also the steering angle sensor etc etc!!

Its no good on S1 cars, you need to connect it directly to the ECu's via the 2 pin plugs in the ECU area..

The "Clones" work Brilliantly!

I also looked at his ABS ECU, but thats about it on XM's... Its more usefull for later S2 Xantias and C5's with All the black box's you ever NOT want!

Paul

[noz]

Hi Paul,

The only trouble is that it won't communicate with the engine ecu of my 1998 2.5TD with the later version of the ecu. It communicates quite happily with my other two 2.5TDs (1996 and 1997).

I've tried my '98 2.5 with DJ's older Elit and it won't talk to it either. I need to now take my Lexia through to DJ's to try it on a few of his XMs. He has a late 98 one too and so I'll need to swap components around to identify the source of the problem.

Other than that it works just fine with all the ecus in an XM.

Cheers

noz

[noz]

Lez,

As far as I can tell it works with all ecus (except the late 2.5TD ). Absolutely no manual came with it whatsoever.

Curious as I am, I opened up the interface box and confirmed my long held suspicion. The (non-multiplex) Xm has many ecus. Without multiplexing the pairs of communication cables must arrive at the 30-pin socket separately and be terminated to individual pins. If the reading device is able to talk to all of the ecus how does it do it if the individual comms lines are all on seperate pins? The answer....very simple and very agricultural. There is only one protocol chip. A bank of relays decides which pair of pins is connected to the protocol chip at what time. If you select for example the ABS ecu on the Lexia software then the relay which connects the relevant pins on the plug to the protocol chip is activated. You can here a relay click every time a new function is selected on the laptop. Only one relay is activated at any time.

Inside the module there's two circuit boards. One circuit board is dedicated to the bank of relays. The other has the command and protocol chips and the USB connector chip. I'll take a photo if I remember and post it here.

I tried for a while with a friend who's an electronics buff to build a circuit to sniff the packets on the comms line. I had a plan to have the dot matrix display show all sorts of car data live including faults, suspension sphere status, injection timing, turbo pressure etc etc. Its still a long term aim but would need a lot of work. The problem is that the packets sent out by the interface to the device and from the device back to the interface with the reply are coded. So there's no way of knowing that a particular digital word is the query and therefore when the reply comes you don't know to which question it was replying. If you have a better idea how to decode the packets then I'm all ears. If you thought you stood a chance I'd even be willing to post the interface down to you on loan.

Ideally, if we could decode all the queries and the replies we could programme a PIC controller and associated memory to handle the comms between each of the ecu comms pairs and send the info to the dot matrix, or in your case the digital dash. What do you think?

cheers

noz

[lez]

very much what i was thinking of, the ecu's probably all have there onw sily twisted standard, but will all share some conmmon theme of question answer protocol, some, like engine ecu on some, just send the data non stop, i suppose that there is so much data, waiting for a question means by the time you have decided what the question is, and got the data, and then sent it, its out of data..

i did find a webpage or two on the fenix 3 ecu used in renaults, that sends data out at 62550 baud i think it was, an odd non standard value if ever i saw one.

unfortunatly while the ecu is exaclty like ours, app ours does not spit the data out, the routines to send the data in the firmware of the ecu just dont exist.

When i have finished my alarm project which i restarted a few months ago with a totally new build/sofwtare, i'll be having a play with ecu's

maybe i should just build a new ecu.....
After all the modern pic chips are more than fast enough, and have enough facilitys, and making a spark / pinging an injector is not that hard....

all it has to do is measure manifold pressure and pedal position, wait for TDC pulse, then wait a short time choosen from a table, to decide when to spark, and read a value from another table for injector opening time...

check lambda sensor every few seconds to see how were doing, and if rich / lean add a correction to the injector timing.

it could even have an mot mode were it runs on as little fuel as possible .....

Now an engine ecu with built in economy/normal/sport settings for acceleration, oh i'm getting an itchy soldering iron just thinking about it..

[robertxmb]

Hi Noz,
First good to see the site back up and you back posting. Both were badly missed so thanks for persevering with the recovery of this valuable resource.

I was very interested in your post about the “Chinese Lexia” as I was toying with the idea of buying one although I have never used anything similar before and know nothing about them. I was dismayed to learn that the device would not work with your later 2.5 XM, as I too have a 1998 reg. XM, a 2.5 exclusive RP 7266 and would be interested to know if mine is unlikely to talk to it either. Unfortunately I am too far away to take up your offer to call by and try it but I would like to hear if you manage to resolve the problem or find a workaround.
My car computer details may be useful for comparison with your 1998 model, or indeed, other late XMs you may get an opportunity to try. Here goes :-

Main ECU BOSCH L3 also marked L3.17 after the first bar code and MSA 11.L3 before the second bar code.

Suspension ECU Valeo H5 S2 J2G

If you can shed any further light on the problem/solution I would appreciate any such information in due course.

Best regards,

Robert.

This post has been edited by robertxmb on May 06, 2010 12:43 am

[citroenxm]

Were are you Robert?

Ive one of these Lexia copies, and works extreamilly well with late 1999 Xantia HDi's, so I cant see why itshouldn't work with a 2.5 of any sort!

Paul

[robertxmb]

Hi Paul,

Near Enniskillen !!!
Yes, I would feel a bit miffed if they could not read the later 2.5 ECU so perhaps someone with the same ECU as per my details will advise, including yourself if you get an opportunity to test one. Noz could read the earlier 2.5s but not his 1998 reg.

Thanks for response.

Robert.

This post has been edited by robertxmb on May 06, 2010 11:40 am

[robert_e_smart]

Another XM owner in Northern Ireland!

Where abouts near Enniskillen are you?

I'm over at the other side, near Newry, but I am reguarliy at my friend's boat in Kesh.

Sorry, I can't help with the vehicle diagnoistics however.

Regards

Robert

[robertxmb]

On the outskirts, not far from Donnelly Citroen,you probably pass them on your way to Kesh. I see one other XM occasionally but don't know the owner. Not many left here but you never know!
I will try a PM from the other board in the next day or two as the one here appears not to work at present.

Regards,

Robert.

[robert_e_smart]

One of the mechanics at Donnelly's has a black 2.1 TD hatchback. (Well he did the last time I was there, at the Citroen 90th birthday celebrations last year).

E-mail me on robert dot e dot smart at gmail dot com

Regards

Robert

[oh4ndu]

What version of Lexia software you use? This is the first time i hear that Lexia would work with 2.5td.
This sounds almosti too good to be true. Tell me that this is not an april fool.

[noz]

I'd need to boot up the laptop to get the software revision and it has a flat battery at the moment. I will when I get the chance.

I finally got it to talk to the engine management ecu on my 1998 2.5TD. It must have been a loose wire in the 30-pin socket that was preventing it from communicating before.

I can confirm success in communicating with a '96, a '97 and a '98 2.5TD.

cheers

noz

[robertxmb]

Hi Noz,
I think you may have missed my query (posted 5 May) but your most recent post seems to have the answer I was hoping for. I would be grateful if you could confirm that my RP No 7266 falls within the test range of your 2.5 cars. Thanks in advance.

Robert