Help! ABS light is on after cv boot replacement
 

Hi,

I had the cv boot replaced by a local shop. They didn't remove the ABS pulse sensor when they replace the boot. Now, the ABS and brake lights (yellow) turns on after I drive about 100 feet. The lights turns off when I turn off the car. The lights will turn on after I start the car and drive about 100 feet. Now, I cleaned the sensor and unplug the sensor connection but no help. Do you know what's wrong? Is the pulse sensor toast?

Have you tried turning the steering wheel full lock to lock to see if that clears the lights?

Use a code reader and read codes, clear codes, only after you verify that the ABS sys is OK. Then clear the OBD II codes, drive and see if codes return. It could also be a faulty sensor, or check the sensor connectors. I bet they disconnected the sensor without disconnecting the battery first.

Regular OBDII code readers ONLY reads engine codes, will not read the DSC system codes. You need either a really expensive reader with European software or BMW equipment like the GT1 or newer.

Weasel very interesting, I'm not questioning your BMW expertise at all, I know you are one of the best BMW techs. But couple of months ago my ABS light came on after a heavy rain storm. I used my ACTRON OBD II code reader and was able to clear the codes, and the ABS light has been fine ever since.

I disconnect the battery and reconnect. The lights showed up after I started up the car. I drove a block and the lights went away.
I guess it did the trick.

i removed mine when i did my cv boot. maybe it was damaged or a bad connection.

The good ole "Control+ALT+Delete" A reboot always helps!!

May have just been coincidence then... because I wholeheartedly assure you actron does not make a code reader that reads ABS or DSC codes, especially so on European cars. Even the better code readers that do read ABS codes (I have one) only read domestic and Asian. It was most likely just the new key cycle that took away the DSC light, or turning the wheel from lock to lock etc. that cleared it, but the OBDII reader didn't.

WAH.... The lights came back on again. Do you think any local shop will have the reader. I don't really want to go back to the dealer.
Do you think I should replace the sensor? Somehow I couldn't find the sensor for sell on online.

Another question. I also had the control arms replaced on both sides. So the alignment is off. Do you think the lights are related to the alignment?

thanks

UPDATE --

I just had a wheel alignment and the lights went away. I guess the problem was on the speed sensor. Since the alignment was off, the sensors detect different speed on each wheel.

Anyway, if anyone see this problem in the future. They know what's the cause. :thumbup:

It most likely wasn't a wheel speed sensor in your case, but the steering angle sensor. When you had the control arms replaced and the alignment was off it can cause the steering angle sensor to see the steering wheel as turned but the DSC sees the vehicle as traveling straight through the wheel speed sensors. This causes a plausibility fault. Once the alignment was done and the steering wheel was once again straight the plausibility fault isn't present anymore so the warning light goes off. The fault code will still be stored in history codes in the DSC till they are cleared with a GT1 or other BMW software.