Brake pad wear warning light on

[GregD]

Hi,

My front brake discs were pretty much worn out, although the pads were not completely worn and the brake wear indicator on the dash was not showing.

So, at the weekend I replaced the discs as well as the front brake pads, wear sensors and fluid.

Since then the brake pad wear indicator light on the dash has been permanently on, although clearly the pads are brand new (and the ones on the back are approx 50% worn so should not trigger any warning).

Is it necessary to perform some sort of reset on the wear indicator when replacing the pads, or is this as straightforward as a dodgy connection on one of the new wear sensors?

Thanks

Greg

[fastboydave]

Sounds like bad connection/faulty sensor on the new sensors you put on. Alternatively, it could be pure coincidence that the rears have gone too?? You say you have checked, but both pads per corner?? Try puttin the old sensors back on too without fitting to pads and see if the light goes off, then theres your answer.

[azzar0]

You can disconnect the front sensors one by one, until you find the culprit. Unless the rear pads just reached their limit, you probably have a faulty sensor. Even if the rear pads are starting to wear out the light would not be on continuously on the dash. It usually comes and goes in the beginning. When it is on all the time it's time to change the pads, but it can take up to 5,000 from the time the light first comes up.

azzar0.

[Baconaire]

If you are the type to watch your brakes, you can simply remove the sensors altogether (I've been told). If that does not alleviate the problem it must be something deeper in the car and not the sensors. There is no computer reset needed on the sensors. Now if you had a light and did not replace the sensor, that would make the light persist. Once a sensor triggers the light, it needs to be thrown away.

[Loren]

The sensors are just wires - that when worn through trigger the light.

So, if you want to bypass them you will need a wire jumper at each wheel -- or buy new sensors and tie-wrap them away from any moving parts.

[GregD]

Ok thanks all. I'll have to do some investigating next free weekend but it doesn't sound too serious....

[Glyn]

AS Loren said.

The sensors are not sensors in the way most of us would view a sensor.

All it is is a wire that has a bit of plastic stuck onto the end, this end pushes into the brake pad, when the pads wear the disc wears through the plastic and once the disc makes contact with the wire it allows the circuit to earth, Earthing the wire activates the light.

As has been said, disconnect one wheel at a time and check the light, when it goes out you will know where the problem is, simply find where the cable is going to earth and you will have fixed the problem

[JemHayward]

I have a 2003 UK spec Boxster S. My brake warning light came on when on holiday, and as my font pads were relatively new, I assumed the rears were at the limit. So I ordered new pads and sensors, fitted them today, but the old pads were not worn down to the sensors. I've now checked all four sensors, and all pass a current, and all seem to be plugged in to their sockets securely. Where else can I check, as it looks like the circuit is broken somewhere else?

[Loren]

I have a 2003 UK spec Boxster S. My brake warning light came on when on holiday, and as my font pads were relatively new, I assumed the rears were at the limit. So I ordered new pads and sensors, fitted them today, but the old pads were not worn down to the sensors. I've now checked all four sensors, and all pass a current, and all seem to be plugged in to their sockets securely. Where else can I check, as it looks like the circuit is broken somewhere else?

Are you sure it is the pad wear warning and not low fluid warning?

[JemHayward]

I have a 2003 UK spec Boxster S. My brake warning light came on when on holiday, and as my font pads were relatively new, I assumed the rears were at the limit. So I ordered new pads and sensors, fitted them today, but the old pads were not worn down to the sensors. I've now checked all four sensors, and all pass a current, and all seem to be plugged in to their sockets securely. Where else can I check, as it looks like the circuit is broken somewhere else?

Are you sure it is the pad wear warning and not low fluid warning?

The dash says "service warning brake pad wear" or similar. Brake fluid level is ok, as I checked that when doing the pads to make sure I didn't have too much!

[Loren]

The signal also passes through the PSM circuit - so you can check that too.

From the PSM pump it goes to the instrument cluster.

[JemHayward]

Mine hasn't got PSM.

[Loren]

Sorry, - my typo -- I meant ABS.

[JemHayward]

well, no ABS warnings and the ABS is working ok, not sure where the ABS unit is - its it easily accessible? This must just be a broken or disconnected wire somewhere. I know it goes via a 21way connector near the DME unit, but the wires around that area look ok.

[Loren]

It will be in the front boot - left side under the carpet.

[JemHayward]

I'll have a look for it one evening this week... what colour is the cable I'm looking for? I know its black/brown at the 21 way connector at the back.

[Loren]

It might be easier to trace back from the cluster.

Ohm meter at cluster (brown/black) and then test to each wheel.

The circuit is a loop - 4 solid wire sensors at the pads and their connectors at each wheel - then a single wire to the instrument cluster.

So if any part is broken (open) then it will display as pad wear.

[JemHayward]

That was my plan for next weekend - take the sensors out and test to see if the wheels are connected together in a loop... All four sensors are ok, but getting all the wheels off in one operation requires hardware I haven't got at home.

I may pass the problem on to my dealer, as the car will need a service next month anyway!

[Loren]

I would be willing to bet it is a bad connector on the car - at one of the wheels. Lots of road debris and potential for corrosion.