Citroen XM Forum

My 1993 XM with Bendix system had a rear ABS sensor replaced.

We installed a sensor for a VW golf 3. However, the new sensor has a resistance of 1100 ohm where the original had 2000+ ohms and I suppose that is the reason why the system still throws an error and the ABS light is displayed when the car reaches a speed above 20 km/h.

Does anyone here have experience with this? Could the solution be to replace the other rear ABS sensor, which has the 2000+ ohm resistance with the same type as the new one, so the pair of sensors have the same ohm resistance?

Or could I simply solder a 1000 ohm resistor into the wire of the new sensor to increase the resistance and fix the problem?

In my experience the Bendix Ecu can accept 1100 Ohm, or 2200 Ohm sensors randomly.

As your car passes the static test I don't think this is a sensor resistance issue, more likely there is an issue with the sensor reliably reading the reluctor ring signal.
Check for a crack in the reluctor ring.
You could swap the rear wheel bearing assemblies, complete with reluctor ring, and see if the fault remains the same, or moves. It has been known for grease in the bearing cavity to cause corrupted reluctor readings.

An oscilloscope would reveal any difference in sensor outputs. These are simple analogue sensors, so the voltage and frequency varies with vehicle speed. As long as the Ecu sees a sine wave voltage above a minimum value and all four match, it should be happy.

I take it you have read the ABS codes, to ascertain which sensor is faulty? What code was revealed?

Thank you, Dieselman, for your reply!

To be honest, we have not read any codes, since there - to my best knowledge - are no readers available for this car in the area where I live. And I do not have one myself.

What we did initially was to measure the resistance in each sensor and replace the one, which was completely dead.

That solved the issue that the warning light would turn on immediately after the car was started (and before it started to move).

Now that problem is solved, but as mentioned, the light comes on after the car reaches a certain speed.

The difference in resistance between the rear sensors as reason for the malfunction was a tip from a local garage.

But it definitely makes sense to check the reluctor ring, and I will do so now!

There are readers, but it is not just plug in and see all, it is plug in different spots to get different readings

A DIY Blink Code reader is all you need for your car.

See thread viewtopic.php?f=8&t=7368