ABS not activating
Thread Starter
Junior Member
Joined: May 2018
Posts: 49
Likes: 0
C240
ABS not activating
Hi everyone. My ABS will not activate under hard braking. I put in stainless steel brake lines, pads, rotors and new brake fluid. Lateral acceleration sensor shows a value of -2.2 Grad/s when the car is stationary. I cleaned out the component and connector but no joy. I've also disconnected and cleaned the ABS module from the ESP. The wheel speed sensors initially were all showing a positive, albeit static value of .59km/h prior to cleaning the ABS harness however since went back to 0km/h. Fuses all also appear to be healthy and functional.
I've been reading that the brake light switch may be the culprit here. Does the ABS need to be bled as well? I have Xentry/DAS but can not locate any procedure for this. I've read that the ABS block is integrated into the whole system and a regular bleed should remove any air in the module...Thank you for your help I'm advance. Be well!
I've been reading that the brake light switch may be the culprit here. Does the ABS need to be bled as well? I have Xentry/DAS but can not locate any procedure for this. I've read that the ABS block is integrated into the whole system and a regular bleed should remove any air in the module...Thank you for your help I'm advance. Be well!
Last edited by mcc23; May 10, 2022 at 08:55 AM.
MBWorld Fanatic!
Joined: Dec 2003
Posts: 3,275
Likes: 236
From: BC, Canada
2003 C230K Coupe Orion Blue
Can you get the car on a lift and spin the wheels and see if the wheel sensor readings change?
Normally the car will throw an ABS error if something is off. If the wheels aren't slipping then ABS also won't kick in. Remember that ABS only reacts when it senses a difference in wheel speeds. I remember one time I locked all 4 wheels (rainy road) and ABS did not go off at all.
Normally the car will throw an ABS error if something is off. If the wheels aren't slipping then ABS also won't kick in. Remember that ABS only reacts when it senses a difference in wheel speeds. I remember one time I locked all 4 wheels (rainy road) and ABS did not go off at all.
Last edited by slammer111; May 16, 2022 at 07:11 PM.
Thread Starter
Junior Member
Joined: May 2018
Posts: 49
Likes: 0
C240
Can you get the car on a lift and spin the wheels and see if the wheel sensor readings change?
Normally the car will throw an ABS error if something is off. If the wheels aren't slipping then ABS also won't kick in. Remember that ABS only reacts when it senses a difference in wheel speeds. I remember one time I locked all 4 wheels (rainy road) and ABS did not go off at all.
Normally the car will throw an ABS error if something is off. If the wheels aren't slipping then ABS also won't kick in. Remember that ABS only reacts when it senses a difference in wheel speeds. I remember one time I locked all 4 wheels (rainy road) and ABS did not go off at all.
Thanks for the reply. The front wheel speed sensors have been cleaned recently, however there is either rust or something else built up around the rings where the mounting bolt goes through. It doesn't come off with scrubbing. I suppose this could be my culprit...
Also, the resistance in the ABS/ESP module for the lateral acceleration/rotational speed sensor (PIN 29 AND PIN 25) was 2.5 ohm over the threshold! (127.5 ohm). Also, the values for the lat. Acceleration and rotational speed (Grad/s) are NOT 0 when the car is stationary. It basically is spazzing out. I'm keeping an eye on this.
Xentry pointed me to a faulty control module, but I think I will replace the wheel speed sensors first then revisit. Your feedback is appreciated!
Last edited by mcc23; May 17, 2022 at 08:34 AM.
Thread Starter
Junior Member
Joined: May 2018
Posts: 49
Likes: 0
C240
Just wanted to update this thread. I've replaced all 4 wheel speed sensors and the ABS appears to be functioning for the rear brakes now, however not in the front. Insight is appreciated. Thanks
Last edited by mcc23; Jun 23, 2022 at 06:04 PM.
Trending Topics
MBWorld Fanatic!
Joined: Dec 2003
Posts: 3,275
Likes: 236
From: BC, Canada
2003 C230K Coupe Orion Blue
The car isn't happy. Honestly at this point you might want to see if an indie can read the codes and see what can possibly be wrong. Otherwise you're looking at a new lateral/rotational sensor. These things can go bad but it isn't too common. I'd pick one up online or from a local wrecker. Just make sure the PN is the same or at least compatible. The dealer will be able to tell you which PNs will work if you give them your VIN.
I assume the brake system has been bled properly? I remember reading somewhere that the ABS module really does not like air bubbles. As in this model car is particularly unforgiving.
I assume the brake system has been bled properly? I remember reading somewhere that the ABS module really does not like air bubbles. As in this model car is particularly unforgiving.
MB World Stories
The Best of Mercedes & AMG
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Mercedes Teases Updated EQS With Steer-By-Wire and a Yoke
Verdad Gallardo
8 Mercedes Models With Poor Reliability Records
Verdad Gallardo
