Fitting an ABS ECU

steviewonder7 · Unread post by **steviewonder7** » 05 Feb 2006, 19:46

Hi Folks,

Is there a correct way to fitting an abs ecu from an electrical point of vew?I fitted a known good unit today after disconnecting the battery first and reconnecting the battery last.Is this incorrect ?
I say this because my abs still does not work.All the sensors are o.k (two are new) resistances within tolerance,dash lamps o.k.
I was just wondering if I might have caused the abs unit to fail by incorrectly fitting it.
Any ideas folks?
Thanks for your replies in advance

AndersDK · Unread post by **AndersDK** » 05 Feb 2006, 21:16

Yeah well -

Hold your breath, use rubber gloves, and prepare 4 muffins in a square to store the ECU on. These modern Electronic gremlins are screaming sensitive ...

Nope. Modern Electronic units for cars are indeed VERY durable and in-sensitive to handling. I sincerely doubt there is any problem with either of your ABS ECU's. These words comes from old electronics engineer ...

You really have taken extreme care the way you plugged it in. Well done.

How does the ECU tells you there is an ABS problem ?

wheeler · Unread post by **wheeler** » 05 Feb 2006, 21:50

is the ABS ECU & relay getting all its feeds & earths ?

steviewonder7 · Unread post by **steviewonder7** » 05 Feb 2006, 23:33

To answer your question Anders,I believe the abs indicates a problem by
lighting up the abs warning lamp on the dashboard.This is not including the abs system check when you first turn on the ignition key(which I dont get when I turn the key:Abs dash lamp is o.k).Please enlighten me if I've missed anything.
To answer 'wheeler's' question (a) I'm not sure which is the abs relay as there is more than one relay by the electrical gubbins near the fuse box/abs ecu/glow plug relay etc.(b) all the necessary earths check out o.k.
Chasing the wiring to find the abs relay I believe means I've got to disturb/cut into the wiring harnesses,something I loathe to do for fear of creating even more problems for myself.I could pull out the various relays but what will that achieve?
Does anyone have the peugeot 406 haynes abs wiring diagram they could email me as I believe it will help get me a little further diagnosing the problem?Xantia wiring in haynes manual is incomplete

Cheers Steve

steviewonder7 · Unread post by **steviewonder7** » 08 Feb 2006, 22:54

Can anyone give me a clue or even tell me which relay is the ABS relay ...Please

Thanks

AndersDK · Unread post by **AndersDK** » 08 Feb 2006, 23:49

Sorry -

Dont have a Xantia myself - but a Haynes. But the BOL help is as you imagine.
Must be 2 fuses : 1 for the ECU and 1 for the valveblock which is fed via the relay we cant find.
Note that the ECU also checks continuity thru the valve block connector and the valve actuator coils.

But at least I've put your topic on top of the list for a while.

steviewonder7 · Unread post by **steviewonder7** » 09 Feb 2006, 22:07

Thanks Anders,something to think about,and as you mention the Haynes bol is useless in this department as is another manual I have .
Must be a proper workshop manual for these vehicles somewhere

steviewonder7 · Unread post by **steviewonder7** » 09 Feb 2006, 22:11

Is there an exploded diagram of the valve block somewhere? Does anyone know of any diagrams hiden away somwhere on this planet in a cubbyhole

AndersDK · Unread post by **AndersDK** » 10 Feb 2006, 00:07

This is not your wanted documentation - but at least some bits & bops.
My hope is it may inspire you to get a few steps further :
http://www.rwbsmith.plus.com/citroen2/Brakes/abs.pdf

This schematic for the XM ABS inspired me :
http://citroeny.cz/servis/xmser/elektro/schema_ABS.jpg
You can see a dotted frame around the valve actuator coils - and a relay icon within that dotted frame !
This means that the relay is to be found on the valve block itself !

May certainly not be the same for the Xantia - but try look for it there !

steviewonder7 · Unread post by **steviewonder7** » 10 Feb 2006, 11:35

Thanks for that Anders,very generous of you to spend the time helping me out.I'll have a closer look at the diagrams and see what I may or may not find.
Thanks again

PowerLee · Unread post by **PowerLee** » 11 Feb 2006, 17:35

steviewonder7 wrote:Hi Folks,

Is there a correct way to fitting an abs ecu from an electrical point of vew?I fitted a known good unit today after disconnecting the battery first and reconnecting the battery last.Is this incorrect ?
I say this because my abs still does not work.All the sensors are o.k (two are new) resistances within tolerance,dash lamps o.k.
I was just wondering if I might have caused the abs unit to fail by incorrectly fitting it.
Any ideas folks?
Thanks for your replies in advance

What exactly is the ABS doing or not doing? Is the warning light working correctly?

Does it stay on?

Does it come on when the car is driven?

Have you checked the alternator isnt under or overcharging the battery?

What ABS system is it? Bosch? Bendix etc

steviewonder7 · Unread post by **steviewonder7** » 11 Feb 2006, 20:20

To answer your questions'powerlee',the abs appears to be doing 'nothing'.
The abs warning lamp in the dashpanel does not light one iota at any time.
How would overcharging the battery affect the abs ??Battery appears to be in good working order.
The abs ecu in question is the early ATE variety.

Today I made some headway but the abs is still as dead as a DohDoh.
There was no earth from pin 16 in the abs ecu 37 pin plug.So I made up another and spliced it into the relevant cable to pin 16.This made no difference to the functionality of the abs.
I also had the dash panel out to exam the abs warning lamp in greater detail.
12 volts was getting to the lamp,the lamp was exchanged for a new lamp(which had previously tested o.k),12v was exiting the lamp and was getting to the small dashboard circuit board plug(which there are 4 of).From then on it goes into the wiring loom under the dashboard.
As I dont have the correct wiring diagrams I'm unsure where the circuit goes from then on.
I can only summise for now that this part of the circuit is the culprit.
Will have to investigate again in the near future.Work committments are in my way for now.
One other thing,I believe I found the long lost ABS Relay I was pursuing and it was not on top or near the ABS valve block but next to the glow plug relay.I checked that out first thing this morning and it seems to function as it should do.
It appears with all the testing so far that I've carried out thus far that someone else (previous owner or autoelectrician) has been before me.You know the tell tale signs ,if you get my drift.
Oh well....under the dash I go in a few days time to find zee culprit eh?

jeremy · Unread post by **jeremy** » 11 Feb 2006, 22:15

The usual ABS fault is that the light comes on and stays on - as the system detects a fault. If the light doesn't come on then I would suspect the power supply or the ECU itself.

Can I assume that this ECU is functioning in exactly the same way as the first one - ie the light has bever come on?

If this is the case I think you will have to obtain a pin diagram for the multi-plug to the ECU and carefully check if all those that are supposed to be live are and that the connection to the warning light is working.

I do not feel the fault is in the valve block as this would be detected by the ECU which would then display the warning light! I think anything but the most fundamental ECU fault would also put the light on. By a fundamental ECU fault I mean something major dropping off inside.

Overcharging would be generally caused by a faulty control unit in the alternator which in turn may cause spikes which could crash the ECU, - you will know if its overcharging as the lights will work better, the wipers will go beserk and the indicators will flash faster. Incidentally my BX with ABS suffered from overcharging with all the above problems but the ABS light never came as a result.

You state the the new ECU is 'Known good?' - as a matter of interest how was it tested?

PowerLee · Unread post by **PowerLee** » 12 Feb 2006, 10:22

The ABS system has a voltage protection relay built in, If the alternator is under or overcharging or the battery is about f****d then the protection relay will kick in & shut down the ABS system & stick the dash lamp on.

Most owners would notice something was up with the charging system well before the threshold of the protection relay kicking in.

I had an ABS problem on my old 405, Intermittent coming on of the dash lamp, The Pug dealer couldn't find the problem, they changed the brake light switch under the cars warranty lol.
I eventually traced this fault to a lose earth wire up behind some trim in the passenger side footwell, When the wire was moved or the temperature was cold the ABS warning light would come on.
Once I cleaned it up the ABS was fine every since.

No idea who deals with ATE, Shame its not a Bosch system, I could have helped you there.

steviewonder7 · Unread post by **steviewonder7** » 13 Feb 2006, 22:11

Just to answer some of your questions jeremy:-

You can assume the replacement ABS ECU is functioning the same way as the original ecu and that the abs warning lamp does not come on at all.

The replacement abs ecu came from a vehicle with the abs working up until the time of its removal from the said vehicle.

Tommorrow I am going to try and trace the wiring loom from the dash panel to see if there's a break/or loose connection.Hopefully it will be as easy a problem as that albeit awkward.
Thanks for your replies and suggestions thus far people.
Steve

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Fitting an ABS ECU

Fitting an ABS ECU

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