cars ecu has gone wrong again :(

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

Mosser
Posts: 448
Joined: 21 Jun 2004, 01:52
Location: United Kingdom
My Cars:

Post by Mosser »

The strange thing to me, is that there is a 10 amp fuse in the engine bay fuse box that is marked as the ECU fuse, I was assuming that this was the sort of holy grail power feed to the ecu and that if this wasnt there, then the ecu wouldnt run

And it doesnt seem to change anything whether this fuse is in or out of the circuit, the power on each leg of the ecu remains constant which makes me think i am dealing with a really silly fault like a break in the wire, but there are no wiring diagrams for a synergie so i havent tracked this down as i dont know where this 12v feed end up,

I'm going to open the wiring loom up and trace this wire i think and then buzz it through with the battery and fuse out of circuit and see what i can find

I'm starting to wish this was a simple carburettor engine now !! :)
2002 Peugeot 806 quicksilver HDI with bosch ecu
Mosser
Posts: 448
Joined: 21 Jun 2004, 01:52
Location: United Kingdom
My Cars:

Post by Mosser »

Right, just had the battery out and the engine bay fusebox out and checked where the 10 ecu fise goes, and it goes nowhere !!!, the 10a feed goes into a big round multiplug with a twist ring connector only to end at a pin that has no connection by design !!!, Grrr to citroen for putting the fuse in place when they made the car, as it serves no useful purpose
2002 Peugeot 806 quicksilver HDI with bosch ecu
philhoward

Post by philhoward »

Looks like 8200 is the immobiliser (the symbol looks a key and a keypad..) which fires relay 8204 to me.....back round the circle we go!
User avatar
CitroJim
A very naughty boy
Posts: 49531
Joined: 30 Apr 2005, 23:33
Location: Paggers
My Cars: Bluebell the AX, Polly the C3 Picasso, Pix the Nissan Pixo, Propel the duathlon bike, TCR Pro the road bike and Fuji the TT bike...
x 6160
Contact:

Post by CitroJim »

I missed all the fun :) Been out turning up a new Activa Ram Bush on my lathe. More on that story later :wink:

As Phil says 8200 is the keypad (which you don't have I understand) and Relay 8204 is operated by this pad to wake up the ECU. My uderstanding is that when the double relay pulls in another 12V supply is present at pin 35 via a relay contact set on the double relay.

I see no problem in leaving an ingition switched feed on pin 35 permanantly.

before you do that, what do you see on pin35 when the ignition is on?
Jim

Runner, cyclist, time triallist, duathlete, Citroen AX fan and the CCC Citroenian 'From A to Z' Columnist...
dnsey
Posts: 1538
Joined: 20 Oct 2004, 01:39
Location:
My Cars:
x 19

Post by dnsey »

I follow your logic, but if 8204 is the immobiliser relay, it's not very secure! Anyone in the know could do just as you're proposing to hot-wire the car :shock:
Mosser
Posts: 448
Joined: 21 Jun 2004, 01:52
Location: United Kingdom
My Cars:

Post by Mosser »

what i have found out today with the help of people on here, is that i had an immobiliser fault, and with the information i had posted on here, i was pretty much telling people how to bypass the immobiliser so i have deleted my todays posts that deal with that so that this information doesnt become widespread on the internet

I think it would be wise for others who have posted on this thread to check their posts to make sure they havent given away immobiliser secrets too!
2002 Peugeot 806 quicksilver HDI with bosch ecu
jeremy
Posts: 3959
Joined: 20 Oct 2002, 16:00
Location: Hampshire, UK
My Cars:
x 2

Post by jeremy »

I don't think there is really much to worry about - its always been possible to jump start non-immobilised mechanical XUD's with a simple lead with dog clips and I've never heard of it being done. The instructions for removing the later ECU immobiliser for diesels have been here for some time - but like the petrol one it requires dismantling and some detail work.

At the end of the day all cars have steering locks - and few Citroens have any thief cred and could probably be safely left with the keys in them. Your belongings may go but your car wouldn't.
jeremy
lolingram
RIP 2010
Posts: 550
Joined: 27 Dec 2006, 07:59
Location: France
My Cars:
x 1
Contact:

Post by lolingram »

Not being very au fait with IC circuitry (my epoque is 1950s/1960s analogue Colpitts//Williamson/Baxandall thermionic stuff), I would personally go the wayof strapping another 5v feed from somewhere as you suggest...

I must say that I never imagined finding this hi tech interesting stuff on a car forum. I am humbly enlightened, and following with interest - even looked up and re-read 'Understanding Microprocessors' (1978)!
and i'm wondering if it would simply be easier for me to get an off the shelf 5v regulator and put it in circuit myself to supplement whatever in this ecu is failing ?, i have a nice meaty 12V feed comming in that i could tap off of, and there's an 80 omh resistance between 5V and GND so i am thinking its only using about 60Ma ?, so a 2 amp regulator should be more than enough for the job ?
R.I.P. January 2010.
XM 2.1 auto VSX 1996 - Bosch Inj, Xantia HDi 90 estate 1999, Xantia 1.9TD 1997
Previously...
GS 1970, Dyane 1974, Xantia 94 VSX TD, XM 94, 2.1 auto - Lucas Inj, XM 92 2.1 estate - Lucas Inj
User avatar
CitroJim
A very naughty boy
Posts: 49531
Joined: 30 Apr 2005, 23:33
Location: Paggers
My Cars: Bluebell the AX, Polly the C3 Picasso, Pix the Nissan Pixo, Propel the duathlon bike, TCR Pro the road bike and Fuji the TT bike...
x 6160
Contact:

Post by CitroJim »

Another piece of excellent work there Mosser :D

I'm not so sure that it is as easy to hotwire as you may think. On the Bosch Motronic the 205 lads have to shell out £££ to have them unlocked if they don't have the matching immobiliser ECU or keypad and known code. Question is, are they being ripped off :?: :?

Perhaps the Magnetti Marelli is a simpler device although I see there are other connections from the keypad. Maybe these carry a serial code into the ECU and also, the immobiliser relay may well be cunningly hidden in a dark recess of the dash which would make any attempt to hotwire a bit difficult. Fact is, if a thief really wants your car, then it is as good as gone whatever security devices it has on it.

I think Jeremy has a very valid point about how desirable the average Citroen is to a thief. A point in their favour :)

Still, as I say, a quite brilliant piece of work 8)
Jim

Runner, cyclist, time triallist, duathlete, Citroen AX fan and the CCC Citroenian 'From A to Z' Columnist...
lolingram
RIP 2010
Posts: 550
Joined: 27 Dec 2006, 07:59
Location: France
My Cars:
x 1
Contact:

Post by lolingram »

I have just (re) read 'Understanding Microprocessors' - Texas Instruments 1977. Although technology has rushed on since then, this is still valid. My time in electro technology dates from '50s/60s - analogue and thermionic - and I have since been slightly baffled by MOS, GATES, (not the arsehole) PNP, NPN, AND/OR - NAND/NOR.

Not any more. In reality, compared with the old valve (tube) era, the digital bones are simplicity itself. Application is complex however...

Flip-Flop I understand. This was sometimes quite difficult to achieve in analogue days (2 easily swithable stable conditions). Now it is a doddle with 'gates'. By the time the crematorium is nigh, I will know it all (only kiddingjavascript:emoticon(':)')
We are running beyond my knowledge of power supplies now as i always used separate or potted psu's that always got replaced rather than repaired, we only dealt with the logic side and reflow work once the fault was identified, i am wishing i was more inquisitive now when i was working as Harris semiconductors now
:D :) :)
R.I.P. January 2010.
XM 2.1 auto VSX 1996 - Bosch Inj, Xantia HDi 90 estate 1999, Xantia 1.9TD 1997
Previously...
GS 1970, Dyane 1974, Xantia 94 VSX TD, XM 94, 2.1 auto - Lucas Inj, XM 92 2.1 estate - Lucas Inj
Mosser
Posts: 448
Joined: 21 Jun 2004, 01:52
Location: United Kingdom
My Cars:

Post by Mosser »

Heh!, yeah, my microprocessor knowledge is a bit rusty too, not having applied is to any real purpose for about 10 years now!, but i still remember the important bits,

Took to car out for a drive with the jumper wire i mentioned yesterday and it is running really nice again, got rid of all the crap that has built up in the last few weeks inside, gave it a wash and a hoover, fixed the sticky central locking that has been bugging me for the last 6 months, replaced the blown bulb in the glovebox and it is really nice again !! :) , and i dont think the fault is comming back again now :)
2002 Peugeot 806 quicksilver HDI with bosch ecu
Post Reply