Hi all,

For a while now the ABS light on the dash has been coming on intermittently. The frequency has been such that it's no more than a mild inconvenience and turning the ignition off and restarting gets rid of it.

Last weekend I was lucky enough to have the use of an Elit tool (from another XM owner DJ) to interrogate the ECU to establish the cause of the fault. As with 99% of all ABS failures it was one of the wheel sensors. The front nearside to be precise.

I disconnected the ECU. For the Bendix system the ecu is contained in the same plastic box as the engine and suspension ecu's. As DJ discovered recently the ecu for the Teves system is located on the ABS control block beneath the battery tray.

I measured each of the wheel sensors one by one from the connector plug and they all read approx 2500 ohms with the exception of the front nearside which read 3.2MOhms. I disconnected the sensor at the junction at the bottom of the inner wheel arch. I measured the wheel sensor and was pleasantly surprised to read 2500 ohms (thats what they should read). I cleaned up the terminals and spades in the wheel arch connector and put it back together. I remeasured the resistance back at the ecu connector plug and it now read 2500 ohms. So, by cleaning the contacts on the plug & socket under the wheel arch I solved the problem.

Looking at the ecu plug holding the connecting cable to your right the terminals are numbered as follows:

35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19
18 17 16 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01

The terminals for the wheel sensors are as follows:

Left Hand (nearside) Front 35 & 18
Right Hand (offside) Front 33 & 16
Left Hand (nearside) Rear 32 & 15
Right Hand (offside) Rear 34 & 17

Terminal 2 is the switched live through the ignition switch
Terminals 03, 20, 27, 28 are all earths
Terminals 04, 05, 06, 19, 21, 22, 24, 26 are all connected to the ABS control block under the battery tray
Terminal 12 is connected to the diagnostic socket

This information is only valid for the Bendix ABS braking system.

Hope this helps others with the same problem.


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