Brake problem? Need advice please
 

Hi Guys.

I drive an E60 M5 while my wife drives an '09 X5 xdrive3.0d.

Yesterday she got an error coming up on the idrive screen telling her that she needs to replace the brake pads and to take the car to a dealer to do that.

The thing though is that if you go throught the various idrive menus to the brake pads it tells you that the front have something like 20,000km to go and the rears something like 40,000km. This seems strange to me and as if there is an error present.

She uses the car to drive our 4 kids around so if it really is somethign up with the brake pads I want them swapped out without delay. Though it appears to me to be some sort of software malfunction.

What do you reckon?

Cheers.

Could be a sensor error, but I would be checking with the dealer to see what it is.

Are you sure the warning was specifically for brake pads, and not for the brake system in general? Something malfunctioning in the brake system could cause a warning separate from the brake pad life message. Also, the brake fluid is a 24 month replacement item, so perhaps the service warning was related to that?

I checked the error again.

"Brake pads worn
Have them replaced by the nearest
BMW service"

I have completed a visual inspection of the brakes and there is plenty and I mean plenty of meat left. I expect the brakes actually have 20000-40000km left on them.

I should also say that the car only has 35000km (21,000mi) on it.

Further thoughts?

Could be a broken/damaged wire on the pad wear sensor.

IF SO, this is a warranty item- not 'wear and tear'. Kudos for doing your own visual, I suspect the dealer will not be able to hoodwink you...I reckon.

:)

A

I had this error on my E70 and then it went away after a while. I put it down to something getting stuck between the disc and the sensor, possibly some debris from some heavy braking. Anyway a month later and all has been fine no more brake errors and plenty of pad left to go.

If your BMW is under warranty, Take it to the dealer.

That can't happen. When the sensor contacts the disk, it wears through a thin wire and breaks the contact, opening the circuit. That contact can't come back when debris moves.

Intermittent warnings usually have to do with a poor connection in the harness, at the other end to the sensor. If it comes back, just unplug them and plug them back in.

The E70 uses a multiple-stage brake sensor in the pads, unlike the single-stage sensor in the E53. The sensor wears through the nub, that rubs through a thin wire, and an open circuit in the sensor loop causes the brake pad light to come on. There are two separate loops for the E70, in the same sensor, corresponding to two different pad wear thickness measures. The iDrive mileage indicator is driven by these sensor triggers, plus a computer estimate of brake use for interpolation as to life remaining.

I suspect that you have an open circuit in the final step of the sensor, but not in the first step. Thus, the iDrive is estimating lots of life, but the light on the dash is driven by the open circuit for the last stage.

This could be the sensor at the caliper, but I would first check the plug at the end of the sensor wiring harness (opposite end to the sensor). I recall it being in a small junction box on the chassis. I would unplug the sensor there, and plug it back in. I would look for corrosion when I did that. Sensors do not require coding when changed, so you are safe to play with them.