[David_2404]

About 3 months ago, I had front and rear pads on my 2008 BMW 320d replaced at a local garage.

Last week, I visited an independent specialist for a different issue and their diagnostic equipment showed the front pads at 90% and 30% for the rears.

I admit, I don't know if that's the %age used or %age left - either way, it seems a lot for 3 months wear. I'm sure those of you used to diagnostic equipment will know!

Before I make a fool of myself back at the original garage, is there any simple or logical explanation other than I am still driving around on 10 year old brake pads? Could the sensors have not been re-set?

[nsjames]

the service minder is a simple math problem done by the computer.

it doesn't know actual pad wear.

they were not reset.

[Efthreeoh]

Did they replace the brake sensors? It looks like they only reset the front brakes in the CBS and not the rears.

I'd recommend the shop unplug the rear sensor (if it was replaced - it should have been), then plug it back in, turn on the ignition and reset just the rear brakes in the CBS. Why did you replace the brakes? Did the pad replacement service icon come on?

[David_2404]

Thanks for the input

Originally Posted by Efthreeoh

Did they replace the brake sensors?

Not sure if they did - my receipt only shows disks and pads on all 4 corners replaced

Why did you replace the brakes? Did the pad replacement service icon come on?

UK annual MOT test flagged it up as an advisory item (not same garage)

[Efthreeoh]

Originally Posted by David_2404

Thanks for the input

Not sure if they did - my receipt only shows disks and pads on all 4 corners replaced

UK annual MOT test flagged it up as an advisory item (not same garage)

So quickly, here is how the pad life monitoring systems works. BMW uses an algorithm to estimate brake pad wear based on assumed standard use. There is a consumable sensor embedded into the pad (it snaps in) that has two loops of wire. After the 1st wire breaks at a mileage and time point, the algorithm then uses that data to adjust the estimate pad life based on actual use data. Once the 2nd loop of wire breaks, the gauges light with a red "Brake" icon, which indicates the pads need replacement.

The sensors should be replaced any time the pads are replaced. Not changing the worn senors (both loops broken) will not allow the CBS system to reset the algorithm. If your CBS now states 90% pad life left in front and 30% pad life in the rear, something is amiss; there should not be that much difference between the front and rear pads if they were replaced at the same time.

[nsjames]

I had a hell of a time resetting my rear CBS minder after a sensor replacement.

internet told me to remove sensor, shor tthe pins together, reset the CBS and then reinstall new sensor.

so it's quite possible that the shop did reset the CBS, but didn't check that it actually reset.

FWIW the internet recommended procedure did work. Reason for sensor replacement was damaged sensor wiring. Tripped the red brake ligh like the sensor had worn through.