Arrie

Pretty bold statement that "Also the explanation that the ECU uses the ABS wheel speed sensors is NOT correct". Do you really mean that the car's brain does not need to know about wheel speeds and so being does not need wheel speed sensor data?

Or do you suggest that there are two sets of wheel speed sensors in each wheel, one set for ECU and the other for ABS? Take your pick and realize that there is only one set of speed sensors and that THEY ARE NOT JUST FOR THE ABS.

Arrie

Arrie

You said you cleaned fron wheel speed sensors but did not have time to do the back ones.

Now, find time to clean/inspect rear wheel speed sensors. You know how to do it and it does not cost you other than time.

Arrie

Theresias

Nothing bold about the above statement. Descriptions of ESP and ASR functionality can be found in the VW/Audi documentation for the relating systems.

The individual wheel speed sensor values are only used by the ABS/ESP module, the ECU uses a speed signal/value which depending on the ECU programming does not need to be coming from the ABS/ESP. Many ECUs calculate their speed values based on selected gear, gear ratio and engine speed. If you want to test this, unplug a wheel speed sensor and see what the speed values in the ECU measuring blocks do.

Since mlmerwin has not posted real details from his vehicle what we have been doing so far was guessing blind, but it seems that some incorrect conclusions have been drawn by mixing things up.

The 18256/P1848 found in the ABS/ESP is most likely stored because of the 17700/P1292 in the ECU. On the other hand the 18057/P1649 is most likely caused by the 00526 but even that has absolutly nothing to do with the wheel speed sensors. To me this looks like you are chasing ghosts and should be looking at other causes instead.

Arrie

So, now suddenly it is ABS/ESP module and not just ABS. First time I see it is one module that has both built into it.

My intention is not to try confuse anybody. I just know, that ABS works for keeping wheels from locking up during braking. ESP controls wheel slipping the other way, i.e. if wheel spins faster than car speed would allow and this part of it depends on the speed reading from the wheel speed sensor.

If you concider the ESP being part of the ABS module then fine. I still think ESP is part of the main brain of the car and not part of the ABS. I would not be surprised if there was a time that you could buy one of these cars without ESP but with ABS since ABS has been kind of "mandatory equipment" in cars for a long time in a lot of coutries but ESP still is not.

When wheel spins faster than it should it requires engine power control together with braking control and I think the ECU is using wheel speed sensor signals for that.

But that is just my opinion...

Arrie

Uwe@Ross-Tech.com

There is no "main brain" in the car. There are a number of different control modules handling different sub-systems; these modules are effectively peers.

The ECU does not know or care about the individual wheel speeds. On those cars without a separate Vehicle Speed Sensor at the output of the transmission, the ECU gets "composite" vehicle speed messages from the ABS module.

On those cars which have ESP, it has always been a function of the ABS control module. Under certain conditions, it may request a reduction in torque from the ECU, but that's about the extent of the ECU's involvement in the ESP function.

-Uwe-