Abs Installations, Description of Types

[xmexclusive]

Hi All

Have just sent off an XM ABS summary to the CCC XMinations so thought a copy of the salient points worth putting here.

As far as I know there were four different types of ABS fitted by Citroen during the XM production run.

With the 1989 launch most XM models were fitted with a BENDIX ABS installation though a few models were not ABS fitted. To avoid doubt I shall refer to this ABS system as BENDIX 1. It is worth noting that nearly all fault finding guides are based on this early XM ABS.

In the middle of the XM Mk 1 production run Citroen changed to a different BENDIX ABS installation. I shall refer to this as BENDIX 2. The toothed ring on the drive shaft, the sensor resistance and the ABS ECU all changed. The green electrical plugs on the ABS sensor wires did not change which perhaps was a pity because it is not obvious that the two systems are different. There is some compatibility between components from these two systems but also some prohibited combinations.

This same BENDIX 2 installation was used in the early Mk 2 XM's as well as the later Mk 1 XM's. Both BENDIX systems have the inbuilt ABS relay on the ABS block down under the battery. They also have an ABS ECU in the engine compartment 'black box'.

Citroen then changed the ABS to a totally different TEVES installation with different sensors, blue electrical sensor connectors with the front ones moved out of the wheel arch, a combined ECU and ABS block down under the battery box. I suspect that this system has the separate purple relay in the engine compartment. I believe that the change to this type of ABS applied to all models from ORG 6810 and not as is often suggested that the factory fitted whatever was to hand. Most of the TEVES components are actually marked ATE. There is no interchangability between TEVES and BENDIX components. The key identifiers to spot a TEVES installation are blue electrical plugs on the sensor leads, no ABS ECU in the engine compartment 'black box' and the front ABS sensor wires going behind the mud shield at the front of the front wheel arch.

Edit Note added 5/6 Oct 2008: The change over date to TEVES ABS suggested above may well actually have been a little earlier. A forum member has reported TEVES on his 2.5 Exclusive ORGA 6750. I have a BENDIX fitted 2.5 ORGA 6741. Derek reports that his 2.0 Estate ORGA 6764 has Teves so it was not just the 2.5 production that cut over early.

Edit Note added 25 Jan 2009: The Mk2 XM microfiches show separate ABS pipework diagrams for Bendix and Teves with the cut over date shown as from ORGA 6741.

Just to complete the picture in late XM Mk 2 production Citroen fitted a TEVES Mk 20 ABS installation but unfortunately not having owned such a recent XM I know very little about this system.

Regards

XMexc

This post has been edited by xmexclusive on January 25, 2009 01:41 am

[robertmnorton]

Just a quick add, as far as i am aware the TEVES MK 20 uses hall effect wheel sensors and a proportional brake control valve for traction control and MAY have been fitted to the V6 but never on export models.

[xmexclusive]

Hi All

TEVES ABS

I have now found a copy of the Citroen General Specification for the "TEVES" ABS and copy the main points below:

The source document is the 1996 Model Year Presentation dated 31 August 1995.

"BENDIX" ABS replaced by "TEVES" ABS. ( XM all models except XM V6 24S).

It comprises the following units :
- wheel sensors (x4)
- rotor wheels (toothed wheels) : number of teeth 48 (without modification)
- a compact assembly incorporating : an electronic control unit ; the hydraulic
valve block (3 inlet electrovalves, 3 exhaust electrovalves)
- a safety relay (on battery tray)
- a test warning lamp
- a autodiagnostic device connected to the central socket

Location of "ABS" hydraulic valve block (without modification).

Special features :
- no bleeding of the "ABS" valve block
- E.C.U. attached to the "ABS" valve block
- safety relay added to the E.C.U. supply lead (on battery tray)
- new speed sensors

Speed sensors
Supplier : VDO.
Connector colour : blue.
Resistance : 1100 ohms.
Tightening torque : 1 m.daN.
The air gap is not adjustable.
Air gap value 0.58 to 1.95 mm

Connector ;front wheel sensors
Located at the front of the front wheelarch.
Access to the connector : remove the mud shield.

Connector ; rear wheel sensors
Located on the rear axle beam.
Interconnections : (without modification).

Repairs
Precautions to be taken : coat with NORVA 275 grease, the centring bore of the speed sensors.

ATTENTION : Mixing old and new parts is prohibited.

ABS E.C.U.
Identification : label with white inscriptions on a black background.
E.C.U. references : 10 0943 0204 (6).

ATTENTION : The E.C.U.s of CITROEN XM and XANTIA are not interchangable.

"ABS" hydraulic valve block

ATTENTION : The "ABS" hydraulic valve blocks of CITROEN XM and XANTIA are not interchangable.

[xmexclusive]

Hi All

I have now found a description for the BENDIX 1 ECU

ECU - Purpose and operation

* The wheel sensors continuously send signals to the ECU which monitors them and calculates the speed of each road wheel. From this information, the ECU establishes the average road speed of the road wheels and, therefore, the speed of the vehicle. The ECU compares the speed of the vehicle with that of each road wheel and determines whether the wheel be spinning or locking.

* The ECU comprises two micro-processors, a main processor responsible for the checks and calculations of the system, and a second processor with an independant memory. The function of the second processor is to check the credibility of the signals received and sent by the main processor.

The ECU is programmed to control the braking pressure and therefore the speed of the road wheel according to the following general principle:

Initial phase: Under braking, the pressure in the circuit increases to the point when the speed of the road wheel drops below that of the reference speed determined by the ECU.

Phase 1: The speed of the road wheel decreases rapidly to below the ECU reference speed. The ABS system reduces the braking effort on the road wheel by creating a rapid pressure drop in the appropriate circuit followed by a succession of smaller drops in pressure until the road wheel is released.

Phase 2: The road wheel is released. There is a rapid rise in braking pressure followed by a succession of small pressure rises until the road wheel again starts to lock. This ensures optimum braking effort.

At this point, the cycle is complete, the process will return to phase 1 and the ABS system will repeat the cycle until the vehicle comes to a halt.

Regards

XMexc

[xmexclusive]

Hi All

List of Modifications to the BENDIX ABS

Modification of toothed rotors and the ABS ECU from the 1st October 1990, R.P.5075 the rear hubs of vehicles fitted with ABS have been fitted with a new rotor with rectangular teeth. Linked to the above modification, the ECU also recieves a modification, enabling it to read the signals from the new rotors and therefore determine the rotational speed of the roadwheel. The ECU references are different:
Early ECU - S 101 320 001 (BENDIX).
New ECU - S 101 320 002 (BENDIX).
The new ECU has been fitted since 11th February 1991, R.P.5208.

The new rectangular tooth rotors are compatible with both types of ECU.

Only the early ECU is compatible with both types of rotor.

The fitting of a new type ECU to a vehicle fitted with early rotors is forbidden.

As a reference note from March 1991, RP5229, the front brakes of CITROEN XM vehicles are modified. Larger Discs & Pads with Calipers strengthened.

At RP5810 new front ABS sensors were installed. (part no 96 161 385). These new sensors are marked across the rear with "Bendix F" & "SIEMENS" in two separate lines. The resistance reading of these sensors is 2200 to 3200 ohms.

The sensors used up to RP5809 are marked vertically up the rear "Bendix F". The resistance of these sensors is 1000 to 1400 ohms.

The vehicle may be fitted with both types of sensor on the same axle. The sensors are compatible and do not affect the operation of the system.

The rear sensors (part no 96 067 694) were unchanged.

The sensor contacts for resistance testing on the ECU plug are:

N/S/F 35 & 18

O/S/F 33 & 16

N/S/R 32 & 15

O/S/R 34 & 17

Regards

XMexc

This post has been edited by xmexclusive on April 20, 2008 01:07 am

[xmexclusive]

Hi All

BLEEDING the ABS and BRAKES

There ia a full description in HAYNES for bleeding the ABS block and the brakes. The detail is based on the Citroen Workshop Manual instructions for bleeding BENDIX brakes. The order of bleeding is: ABS; RH rear; LH rear; RH front; LH front. As mentioned above with TEVES brakes the ABS block does not require or have provision for bleeding.

Regards

XMexc

This post has been edited by xmexclusive on April 30, 2008 08:51 pm

[xmexclusive]

Hi All

Just a note to say that I have now obtained a Citroen manual for the TEVES 20 ABS system and will update this self help when I get a chance.

Regards

XMexc

[robertxmb]

Hi xmexclusive,

Just a word of thanks in appreciation for the excellent reference material and your research of same.

Robert

[xmexclusive]

Hi All

Following a bit of ABS fault finding by MTXM it seems that the BENDIX ABS block and the attached relay board were unchanged both when Citroen modified the ABS mid MK1 production and also for the early MK2's which were BENDIX ABS fitted.
I will add a note to the help file above when this is finally confirmed.

Regards

XMexc

[xmexclusive]

Hi All

Looks like the cut over from BENDIX 2 to TEVES took place a little earlier than ORGA 6810. I have just got back my SORN 95 VSX 2.5 car that a friend has been storing for a few years now. Its ORGA is 6771 and it has TEVES ABS fitted. Now recently a Forum member, Jackyboy has been successful in repairing the ABS on his 2.5 Exclusive ORGA 6750 and he reports that too has a TEVES ABS fitted. I also have a 95 VSX 2.5 Estate built just over a week earlier ORGA 6741 and that has a BENDIX ABS fitted.

If anyone has cars with ORGA 67xx or 68xx can you please check the ABS type and post the results here. Thank you.

I will check and see if I can track down where my original statement of ORGA 6810 for the change over came from and also make an edit in the original posting that earlier TEVES ABS have been found.

John

[DerekW]

Hi John,

My N reg estate is 6764 and has Teves.

Derek

[xmexclusive]

Hi All

Did a bit of checking following a question on here about using Xantia ABS sensors on an XM. According to HAYNES the Xantia was fitted with the TEVES Mk4 ABS system up to January 1998 with later models getting the TEVES Mk20 ABS system. I think but cannot confirm that the TEVES ABS system fitted to XM's from 1995 is a TEVES (Mk1) ABS system.

John

This post has been edited by xmexclusive on December 28, 2008 06:31 pm

[xmexclusive]

Hi All

Have now found a reference to the Bendix/Teves cut over date for XM's. I was looking through the Mk2 XM microfiches this evening and realised there were seperate ABS pipework diagrams for Bendix and Teves with the change over ORGA given as from 6741. Will update the main entry.

John

[xmexclusive]

Hi All

Now got my hands on a Bendix ABS test manual (Pueguot). Some information I have not found in my Citroen books so will post some details when I get the chance. Seems to suggest that you can set up a switch to get the car ABS light to blink out the faults recorded in the ABS ECU.

John