[dunny87]

Hi All,

I recently had my rear brake pads replaced on my 06 E90 by a friend who is a mechanic. He replaced the rear wear sensor and I was able to reset the warning through the dash. He never changed the front pads as they were only half used, but for some reason the wear sensor seems to still have tripped. In the service log it is now yellow instead of orange and it displays ------ mls.

I have since ordered the front wear sensor but my question is how easy is it to replace the sensor and can it be done without removing the caliper, or better yet can it be turned off completly! I did some searching around and all the DIY threads are for when you are replacing the brake pads so i'm unsure if the caliper needs to come off in order to replace the sensor.

If there are any good links on how to replace the sensor specifically could someone point me in the right direction?

Cheers
Phil

[BKV122]

caliper doesn't need to come off to replace the sensor.

But it sounds like your sensor hasn't tripped, when it trips you get the red BRAKE light and a car on a lift. This just sounds as your cars computer is saying your brakes are due soon and your sensor may trip in the next few days

[dunny87]

Sorry forget to mention the red light is there and the car on a lift too. Thats why I want to change it as i keep thinking i've left the handbrake on! Is it a big job or quite easy?

Phil

[BKV122]

pretty easy to do. Take the wheel off pull the sensor out of the pad, follow the cord along unclip it as you go till you come to a box. Open the box unplug the brake sensor cord and then connect your new cord and follow the clips back clipping the new sensor in and then push the new sensor into the pad , make sure its in there with a little tug.

Might need to use a end of a screw driver to get it in there better

Make sure when you pull the old sensor out make sure the hole it goes into is clear so the new sensor can fit in easy.

[ENINTY]

I don't have direct knowledge of the 320d, but I do for my '06 325i. I am assuming the 320d uses the same brake system with the same functionalities as the 325.

I think you may need to replace the front pads as well. The E90 has brakeforce distribution built into the brake system (your 320d may not) so it pretty much wears the pads evenly between the front and rear brakes. When my pad indicator came on all four of my brakes needed replacing. Once you change the wear sensor it automatically resets the pad wear indicator light (which is different than the CBS brake pad life indictor).

You should remove the front pad sensor and inspect it closely. If your car does not have the brake pad replacement light on (it stays on constantly once it trips) then your front pads are probably close to needing replacement, or the CBS is miscalculating the estimated miles left until replacement is needed. If you put a new sensor in the front pads without replacing them, you will just confuse the system because it uses two stages in the wear sensor to calculate the estimated miles left until the pads need replacing. If you install a new front sensor, it will rapidly wear down to match the level of the already-worn front pads and go through the 1-stage of wear again. You may end up with a condition where the CBS is confused and keeps telling you you need new pads even after you reset everything.

You need to understand that the CBS estimates when the pads need replacing based on a predetermined formula for brake wear and then the distance between when the pads were new and when they reach the first stage of wear (through the wear indicator). The thing you need to know is that when the light comes on that says the pads need to be replaced that is the time the pads have worn down to their minimum limit and need to be replaced; the CBS does not indicate when the pads need replacing, it just estimates the time/mileage when it thinks they will need replacing and is really more for brake inspection rather than brake replacement.

The rule of thumb is only replace the wear sensor when you replace the pads.

[dunny87]

Tried to do this today but could not get the sensor out of the caliper. Any ideas? Does it just pull out or is there a trick in order to get the sensor out?

[ENINTY]

It clips into the outer pad on the pistion side in a "U"- shaped opening it sits in a copper spring clip. Every time I've removed them, becasue of age and temp they crack.

[BKV122]

just yank it, if not try a pliers or screw driver to pry it out

[makkan00]

Sorry to bring this back into life.
I am having slightly different issue.
I have updated my DSC module and after that I have used tool 32 to reset CBS servicing (by mistake).

My front pads had 9k miles left on them, where as rear had 26K miles.
After resetting with tool 32, I have following problems
1- Front pad is showing -----
2- Car in on lift (yellow)
3- Hand brake sigh is yellow
4- ABS light turned on

I am not sure if this is related or not, however I think it is down to front pad sensor.
Is there anyway of writing values back (with tool 32 or winKPF)?

or I should be looking to change the front brake sensor?

[AUDELA]

Originally Posted by ENINTY

I don't have direct knowledge of the 320d, but I do for my '06 325i. I am assuming the 320d uses the same brake system with the same functionalities as the 325.

I think you may need to replace the front pads as well. The E90 has brakeforce distribution built into the brake system (your 320d may not) so it pretty much wears the pads evenly between the front and rear brakes. When my pad indicator came on all four of my brakes needed replacing. Once you change the wear sensor it automatically resets the pad wear indicator light (which is different than the CBS brake pad life indictor).

You should remove the front pad sensor and inspect it closely. If your car does not have the brake pad replacement light on (it stays on constantly once it trips) then your front pads are probably close to needing replacement, or the CBS is miscalculating the estimated miles left until replacement is needed. If you put a new sensor in the front pads without replacing them, you will just confuse the system because it uses two stages in the wear sensor to calculate the estimated miles left until the pads need replacing. If you install a new front sensor, it will rapidly wear down to match the level of the already-worn front pads and go through the 1-stage of wear again. You may end up with a condition where the CBS is confused and keeps telling you you need new pads even after you reset everything.

You need to understand that the CBS estimates when the pads need replacing based on a predetermined formula for brake wear and then the distance between when the pads were new and when they reach the first stage of wear (through the wear indicator). The thing you need to know is that when the light comes on that says the pads need to be replaced that is the time the pads have worn down to their minimum limit and need to be replaced; the CBS does not indicate when the pads need replacing, it just estimates the time/mileage when it thinks they will need replacing and is really more for brake inspection rather than brake replacement.

The rule of thumb is only replace the wear sensor when you replace the pads.

Resurrecting this old post — as experiencing similar issues on my 07 325i. Was told one of my front sensors is showing 9% whereas the pads are at 55%. Technician recommended I would need to get new sensor and have it rewired before the lights can be turned off.

Another Indy garage recommended I just live with the lights on and change out both sensors and pads when they need to be replaced.

As is mentioned above, seems it would make more sense to swap out at same time.

A bit annoying to drive with the red handbrake light on — but maybe that's simplest solution until needing to replace pads? Question becomes how do you know when they need changing, besides just keeping up with visual inspection?

I've also heard about some people replugging their sensors and tripping the wires to get lights off and service menu reset. Any experience with that?

[e91Owner]

Originally Posted by AUDELA

I've also heard about some people replugging their sensors and tripping the wires to get lights off and service menu reset. Any experience with that?

With how cheap and easy it is to replace the wear sensor, I would do that. It is also possible to jump the wires as well, although I haven't done it personally. There are lots of DIYs out there on how to do it.