My brake pad wear light came on today, but the pads only have 15,000 miles on them. I also have the rear sensor zip tied out of the way, so the only way that light should come on (I think) is if the front left pads are worn and need replacing, but the pads look fine and should have plenty of life left in them. Is there anything else that would turn on that light?

I'm currently driving cross country, so I haven't had a chance to pull the wheel off and get a good look at the pad an sensor, so that might be it, but it's going to be awhile before I can really look into this, but is there anything else I should look into? the brake fluid level is good.

 

Brake fluid level low trigger a different light if I haven't mistaken. It happen to me at the track, and not on the light with the symbol of a orange brake disc. I think brake fluid indicator is red.

One possibility in your case may the blue barrel connector for the pad sensor disconnected.

 

Bummer, I was really hoping it might be brake fluid. Thanks, I'll definitely check the sensor, I even ordered a new one so I can replace it, though I'm having serious thoughts bout splicing the wires together and zip tieing the front one out of the way like i did the rear.

All my tools are in the moving truck, and my car is back on the trailer, but I did get to drive the legendary dragon today, so if you're going to get a warning light, it may as well be on an epic drive, right?

 

I got my red warning light doing high G turns. It came and went and I initially thought it was the parking brake. The fluid was right between min and max. I later notice my friend's M3 race car had the fluid sensor disconnected.

 

So an update, but no solution yet. I finally had a chance to pull the wheels off the car, and the brake pads are fine, but surprisingly, so are the wear sensors. neither of them are tripped. So I cleaned the rear sensor connection, and put some dielectric grease in it, reset the light, and took it for a drive. The light stayed off, until I went over a bump. So I'm thinking I've got a short or a loose connection. The rear sensor looked fine, and I went ahead and ordered a new front sensor, so next chance I get, I'm going to swap out the front sensor and give it the same cleaning too, hopefully that fixes it. I'm a little nervous I may have a short somewhere in the car's wiring harness, which sounds like a pain to deal with.

Is there any reason not to use dielectric grease on those plugs? It's not something I know tons about, but it seems like a good idea.

 

Disconnect each sensor separately and see which one makes the light go out. If it was me I'd buy two new sensors, install them, and go on my merry way.

 

O.K. to use the grease on the connectors but nowhere near the rotors or calipers. Me, I'd just unplug and take them off. If you still get a light, you'll know the trouble is upstream in the wiring harness.

 

My take is the problem is not in the chassis harness upstream from the blue tubular connector. Don't forget. When the pads are well the two conductors are shorted at the pad. As you wear down the pad lining you grind away the conductive "bridge" at the sensor.

Modern cars' harness are very well made and shorts are next to impossible unless someone mess with it, or cause abrasion to the wire jacket. I bet a donut to a dollar the problem lies between the blue tubular connector towards the dispensable pad wear sensor.

Again to reiterate, when all is well the two conductors are shorted. An open circuit lights up the pad wear indicator. Also dielectric grease do squad for low resistance contact like this. Just make sure you remove any oxidation at the contact. Dielectric grease only acts as water/moisture barrier but will not improve the conductivity of the electrical contacts.

 

Ok, so I replaced the front sensor, but the light is still coming on, so I ordered a rear sensor, and I'll replace that when it comes. If I just unplug the sensors will the light turn off? I'm not really that concerned about having wear sensors, I'm just tired of seeing that light on my dash.

 

pnwR53S is correct and I didn't explain sufficiently. If you unplug the sensors, you'll need to make a jumper to bridge the two exposed contacts. After doing that, your light should go out, proving that the sensor is faulty. If the light stays on, your problem is upstream.

 

Ah, ok, that makes sense. Well I think I'll just slap on a new rear sensor and go from there. I know that at least one of the plastic clips that holds the front wiring harness for the sensor is broken, I ziptied it a couple of months ago when I was replacing my alternator and changing my coolant, so I'm kind of worried that I've had some rubbing there, but we'll see what I can find this weekend.

 

Well, for the sake of completeness, I thought I would update this thread. I replaced the rear sensor this weekend and double checked the front wiring harness. I didn't find anything that looked out of the ordinary in either place, but for $5 the sensors are cheap.

I know this sensor has been on the car for at least 4 years and 35,000 miles, zip tied out of the way for almost all of that time and never getting close to being activated by a worn brake pad. But it appears that it was the problem, so the only thing I can think of is I had the wire kinked enough to short it out triggering the light. There wasn't anything that I could see wrong with the sensor, but I think a new one has fixed the problem, so I'm happy, and a little sheepish for considering unusual scenarios before I eliminated the most obvious suspects. Thanks for the help though!


ps PNWR53S, your donut is in the mail.