ESP / ABS light comes on intermittently

[HITECH]

I’m confused too, hence why I’m asking on here. This is not a black and white typical sensor fault. There is something else going on but your right if it was a faulty sensor I would see it on the live data

Ide say its the wiring and connector the sensor is plugged into. not the rings or the abs module. Them sensors are sensitive as hell to get damaged. either buy the small connector and wiring back to the abs module or hard wire it thru yourself to the connector for your abs sensor to plug into. There is also a red herring fault with them W04's and the speed sensors. When your battery is struggling to put out correct current for the modules the ABS light can trip on. For some reason i noticed this before on a end of life battery on one. When the guy was blasting his tunes and his battery was going flat. An ABS fault appeared and it would come up as front left speed sensor . Im guessing its because thats the 1st one in the circuit.
To rule it out completely i advise on charging up your battery or trying another battery. Spray the hell out of the connector with switch cleaner too.

 

[sceh]

I have a W204 2011 and have had to change the wheel speed sensors innumerable times. Each time it fixes the problem (ESP/ABS/CRUISE CONTROL etc lights on) However, last week the lights came on, checked wheel speeds with Carsoft, cleared errors and all is OK. Then a week later they came on again - same procedure.
Why? The car has done 50K and is kept in a garage so unlikely to be corrosion so what could this be?
Any clues gratefully received!
thanks

 

[Geordie!]

I have a W204 2011 and have had to change the wheel speed sensors innumerable times. Each time it fixes the problem (ESP/ABS/CRUISE CONTROL etc lights on) However, last week the lights came on, checked wheel speeds with Carsoft, cleared errors and all is OK. Then a week later they came on again - same procedure.
Why? The car has done 50K and is kept in a garage so unlikely to be corrosion so what could this be?
Any clues gratefully received!
thanks

What error is coming up on the icarsoft ? Is it giving you a specific wheel sensor ?

 

[sceh]

What error is coming up on the icarsoft ? Is it giving you a specific wheel sensor ?

No errors and the wheel speeds are all ok. I think it is the turn rate sensor (drehratensensor) but I needs to check in the WS manual. I may repost this as a new thread since it seems to be a common and confusing problem and easily fixed

 

[sceh]

Its a bad contact. Do this:

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I did and it works

 

[sceh]

In general, if it is random, it is a bad contact.
You can get the wheel speeds reading fine in either the Engineering mode or using Carsoft or similar but this does not mean the signal gets to the ESP box. If this is the case, contact cleaning is all you need to do.

 

[sceh]

Just an aside about reluctor rings.
In general for a reasonably well cared for car which has not been driven in water and mud, the reluctor rings never fail but if you really feel you don't want to wast a weekend, do this:

Take out the wheel sensor and peer down the hole with a light. You can see if the ring is rusted to death. The ring should have ridges in it. It makes no difference at all if it is cracked (contrary to popular belief)
Stick a small screwdriver in the hole and rotate the hub and you should feel the ridges and the screwdriver goes up and down.
If you feel or see the ridges ( a bit of rust is irrelevant), it is NOT the reluctor ring. Period.

Next, with the sensor in place, unplug the connector of the sensor to the wiring loom and test the resistance. It should be between 800 and 2000 ohms. If not, bin.
Now test the voltage when you rotate the wheel. This is the hard part since you need to chock the car, put it in neutral and ideally rotate at one rev per second - not easy.
If, however, the engineering mode on the dashboard or Carsoft shows wheel speeds and doesn't show one with zero, it is the connector to the ESP box - clean it with fluid.

The need to change a reluctor ring for the average car does not exist. Indeed changing may do something but most likely just jiggles bad contacts or a bad sensor. The reluctor is a bit of metal which has ridges and the when it rotates the Hall effect sensor detects the change in the induced current caused by the sensor - no more, no less.
If you have ridges, it is OK so look elsewhere