# Intermittent 'check brake pads' light



## wimdows (Sep 1, 2007)

Hi,
Recently the check brake pads light seems to come on. It disappears for some days sometime, and then comes back.
We've taken it to my local Phaeton certified VW dealer and they checked the pads but nothing seems wrong (28,000 miles on the clock). Typically, by the time we took the car to the dealer, the warning light had disappeared again.
Recently - it has come back again, so we're booking it in for another check.
What could the possible cause be? Sounds like some electrical fault, dodgy wire, switch whatever to me. Any advice greatly appreciated.
On a separate note, the dealer did not offer a courtesy car (we did not buy the car with this local VW dealer), but I imagined they have to do that as part of the Phaeton certified dealership, or is this not true?
The car is also still under VW warranty, so what faults related to this incident could I possibly expect to be covered?
Thanks for your time.
Cheers,
Wim


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## car_guy (Aug 19, 2005)

*Re: Intermittent 'check brake pads' light (wimdows)*

I would consider this a warranty issue if the pads are not worn to the point where they need replacement and the brake pad light is on. 
Steven


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## ai guy (Dec 29, 2005)

I had this problem. Had the pads replaced and it went in to the garage a couple of times with no joy. Easy fix is to switch the warning light off. You're not going to let the pads wear to the metal are you? Even if you did, when they do wear down you'll be replacing discs and pads at the same time


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## wimdows (Sep 1, 2007)

*Re: (ai guy)*

Thanks for the reply both.
So, how would you switch the warning light off? Get the dealer to do this, I presume?
Thanks,
Wim


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## chrisj428 (Feb 26, 2005)

*Re: (wimdows)*


_Quote, originally posted by *wimdows* »_So, how would you switch the warning light off? Get the dealer to do this, I presume?

Wim,
If you have access to a VAGCOM, the first post in this thread explains how to disable the seatbelt reminder. Contained therein are also instructions on how to disable the brake pad wear indicator. Change the appropriate digit in Controller 17 (the fourth digit from the right) by the appropriate amount (-1 in this case) and Bob's your Uncle.








Otherwise, have the dealer perform the same. Should take them longer to find the 5052 than it will to actually change the coding.


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## copernicus0001 (Nov 30, 2004)

*Re: Intermittent 'check brake pads' light (wimdows)*

Wim,

I *strongly disagree* with the above posts recommending switching off the brake pad warning annunciator for the following reasons:
1. Your vehicle is under warranty and it should perform correctly. Switching this indicator off does not fix a problem, it is just a way to ignore it. Ignoring a problem is not the proper corrective action.
2. This particular annunciator deals with vehicle safety, in particular, brake pad condition. I would want to be certain that my brakes are functioning properly and are in good condition. In the future, I also would want to know when the brake pads needed to be replaced before all of the pad material had been exhausted.
3. If you have someone turn off the brake pad wear annunciator, it is likely it will stay that way for the life of your vehicle. It is very unlikely that someone (a technician) doing a brake job in the future would re-enable this unless specifically instructed to do so. 

I have a few ideas as to why the annunciator is intermittently being activated:
The brake pads contain a "sensor" which is simply a conductor embedded in the pad material that when worn thru creates an open-circuit condition indicating wear to that point.
1. Perhaps a pad has cracked (the friction material cracked in half). This is not an extremely uncommon occurrence. If so, the "sensor"/conductor may only intermittently indicate an open-circuit condition depending on the proximity of the pieces of friction material.
2. Perhaps a pad is worn out - i.e., worn to the point of just barely causing an open-circuit condition, and due environmental or mechanical factors, the circuit sometimes still registers as a closed-circuit (pad-ok).
3. There may be an intermittent open in the harness of one of the brake pads. The pads have a physical wire harness emanating from them. The mechanical and environmental stresses a brake pad is subjected to certainly may precipitate such a condition. 
I could list a few more ideas as to why the annunciator is intermittently illuminating, however, it is pointless to speculate further; this is ultimately a job for the Phaeton technician to solve. A very thorough examination of the condition of the brake components along with intelligent use of a diagnostic scan tool should isolate the problem.
Douglas


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## stevieB (Jul 15, 2006)

My fronts are 60% worn at 90,000 miles


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## car_guy (Aug 19, 2005)

*Re: Intermittent 'check brake pads' light (copernicus0001)*


_Quote, originally posted by *copernicus0001* »_I *strongly disagree* with the above posts recommending switching off the brake pad warning annunciator for the following reasons:
1. Your vehicle is under warranty and it should perform correctly. Switching this indicator off does not fix a problem, it is just a way to ignore it. Ignoring a problem is not the proper corrective action.

I agree completely with the above. Either the sensor system is malfunctioning (the most likely situation since it was reported that the pads were checked and OK), or the pads need replacement. If the sensor system is malfunctioning, it should be repaired under warranty. If the pads need replacement, they should be replaced and paid for by the owner. It seems pretty straightforward. 
Steven


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## car_guy (Aug 19, 2005)

*Re: (stevieB)*


_Quote, originally posted by *stevieB* »_My fronts are 60% worn at 90,000 miles

Quite remarkable. I got 50K miles out of mine (front and rear) and thought I was doing pretty well. You must rarely use the brakes. I don't want to hear any complaints about how much that brake job costs when it come due!








Steven


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## PanEuropean (Nov 3, 2001)

*Re: Intermittent 'check brake pads' light (wimdows)*

Hi Wim:
The electrical design of the brake pad warning system is extraordinarily simple. A wire (a loop, so to speak) runs from the wiring harness to the two-pin connector of the brake pad, through the pad, then back to the wiring harness. When the brake pad wears sufficiently that the wire in the pad is broken as a result of friction against the disc, the circuit is opened and the warning light comes on.
If the light is operating intermittently, then for sure there is a loose connection. My guess would be the connector at the brake pad itself. I don't think it should be too difficult for your VW dealer to identify which pad is the problem (the diagnostic scan tool will provide that information), then to troubleshoot the circuit.
The photo below shows both an old and a new pad... you can see the cable going into the pad, and the connector on the cable. I would suggest troubleshooting start at the connector... just take it apart and check for continuity through the pad. If there is continuity through the pad, then the problem is likely with the wiring harness connector.
Michael


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## wimdows (Sep 1, 2007)

*Re: Intermittent 'check brake pads' light (PanEuropean)*

Thanks to all of you for your incredibly informative and helpful replies.
It may be quite tricky to isolate the problem to one particular brake pad though, as it does happen intermittently. Sod's law says that when the dealer hooks it up to the diagnostics utility, the fault isn't happening, and they won't be able to work out which pad is playing up.
Having said that, checking the connectors into each pad seems a good way to start if the fault doesn't rear its ugly head when at the dealer's.
I may casually copy and paste some of your suggestions and print it out on one sheet and hand to the dealer. I'll be careful to apply some tact in the way I do that. ;-)
Thanks again - this is one great community!
Wim


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## Victor R (Jan 7, 2010)

Hi all,

After the winter we had here on the East Coast, there is an incredible number of pot holes on most roads in my area. I have adapted a "slalom"-like way of driving to avoid these, but it is impossible not to occasionally hit some dispite all precautions and care.

What has happened on several occasions when I do hit one is that my "check brake pads" warning light comes on. (It doesn't happen every time and may be related to the degree of the shock of impact, but I am not entirely sure about that. I really do try to avoid the #*&%ing things, but it is impossible...) This then stays on until I turn the car off. On restart, I no longer see the warning, and it stays off until I once again hit a pot hole.

The interesting thing is that this happens on both of my cars. Both do not have a problem with brake pads; I had them checked.

I am curious if others have seen this behavior. For now, I am just attributing this to another Phaeton gremlin and am not particularly worrying about it...

Victor


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## PowerDubs (Jul 22, 2001)

Victor,

The pad light is triggered normally when the pad wears through a 'wire loop' deep in the pad near the packing plate severing it's continuity.

If the pads are healthy, the suspect are would be the connection where the pad sensor plugs to the car. 

Given the occurrence when jarred heavily, this connection may be corroded or loose.

If it bothers you enough, and you don't need a computer to tell you when the brakes are due, you can simply cut the wires to the pad and twist them together. (solder, heat shrink, etc)

This is fairly common on cars that go to track days and may be running pads that don't have sensors in them so guys make 'bypass plugs' to keep the light away. I believe there are even commercial products sold to do the same purpose.

You can tell by feel driving the car if it needs brakes without a light well before it would ever become unsafe. 

:thumbup::beer:


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## PowerDubs (Jul 22, 2001)

BTW- I didn't scroll up and read the prior responses until just now. I just clicked the thread open read your post and responded.


Sorry to regurgitate what was already said a few times.


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## Victor R (Jan 7, 2010)

Thanks, Josh

The above discussion related to newer cars. Your explaination makes sense for mine, now nine years old. It was the fact this was happening on both that had me puzzled.

Personally, I do not like disabling features that came with the car. The only one I have disabled to date is the automatic rear seat headrest elevation when someone shorter is seated there, and that simply entailed removing a fuse that can easily be re-inserted.

I will live with this for now, and perhaps look to have it repaired sometime in the future should the problem persist. It is more annoying than an issue...

All I can do for now is hope they fix the roads. (It mainly happens on one stretch of US 309 where even driving slalom-style doesn't avoid all of the pot holes. The posted speed limit there is 55mph, which everyone ignores, and one is subject to a great deal of scorn and abuse from fellow motorists if one drives slower than traffic ...)

Victor


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## Victor R (Jan 7, 2010)

I thought I would post a  follow-up.

Once the roads were repaired, the problem resolved itself on its own on my 5-seater (which has 100,000 more miles on it than the four-seater). I have no idea how or why this happened, but... problem resolved. The problem, however, persisted on the four-seater.

The warning would disappear when the car was turned off. It then would reappear if I hit any bump while driving, only to disappear again when the car was shut off. I had new brake pads on the car so I knew it was a 'glitch' and lived with it until it became just too annoying. When I initially took it in to the dealership before a planned 2,500 mile road trip, the main mechanic who works on my car was out, and the fill-ins were scratching their heads, so I kept driving it as is.

At time the car had to go back in to the dealer for routine maintenance and the required annual inspection, I asked them to look at the problem again. They did, initially not finding anything wrong until I asked them to drive the car over rougher roads to hit a bump. This reproduced the problem, but, apparently, no record of this fault is stored anywhere so the computer scans were not helpful. I was then offered two options for resolution: 

Disconnect the system so there would be no more warnings.
Replace rotors and brake pads on the two front wheels as the rotors, while not a "problem", were perhaps cutting into the pads... (The ones on the rear wheels looked perfect.)
Option one was not to my liking as I hate disconnecting any OEM functionality (see TPMS).
Option two would have cost over $700 with no guarantees this would fix anything.

At this point, I printed out this entire thread and asked my service advisor and mechanic to please look at the information here. (My experience in the past was that dealerships, in general, take very poorly to customers telling them what is wrong, sneering at forum posts. "Copping a 'tude" as my kids would say.) My advisor and mechanic, however, were quite receptive. On pursuing the corroded wire theory, the problem was found - on the driver-side rear tire. Repair cost - $50. 

They were all smiles and said this was a good "learning experience". My baby is back to herself. Win-win!

Score one for the forum!

Victor


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## PowerDubs (Jul 22, 2001)

Victor R said:


> I thought I would post a follow-up........ My advisor and mechanic, however, were quite receptive. .......On pursuing the corroded wire theory, the problem was found





Yea!!


Glad the problem was solved. Glad the dealer wasn't 'above' looking for help.


On my wifes GTi, we recently had a problem with the ABS light coming on. A scan showed a faulty ABS sensor.

I replaced the sensor, but the light remained after clearing codes. I bought a replacement 'repair' ABS harness and spliced it into the system for that wheel and the fault went away.

Although it is not common to have a wire harness go bad, it is possible..especially given her GTi has over 240,000 miles on it.


She just picked up an Audi TT last weekend though, and is loving it.


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## Victor R (Jan 7, 2010)

Thanks, Josh.

Appreciate the help.

Victor

I can only hope to get 240,000 miles on my Phaetons...


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## West Country (Jan 4, 2012)

I have been having the 'Check Brake Pads' warning for a while even though my garage told me the brake pads weren't even half worn.

It eventually turned out on inspection that the fault lay with a corroded terminal on the front left. The garage cleaned the contacts, and hey presto problem gone, though they did say that if the fault returned they would need to fit a new left front strut wiring harness.

So this is another source of the 'problem', and might explain eg intermittent manifestations, going over bumps etc.

Edmund


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## W8CMP (Mar 20, 2004)

Mine does this - the brake wear warning comes up on the dash display whenever I inadvertently go over a large bump in the road (right front wheel I believe). After 30,000 miles since the last replacement, the pads are at 50% worn front and back as at the last service in November.

Chris


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## Motorista (Oct 28, 2005)

*I agree: disabling the light is a bad idea*

I totally agree with Douglas: disabling the sensor light is a very bad idea. 

In my experience the problem that you are reporting is very rarely due to an open circuit in the sensors harness. Most often it comes out of the rotor becoming worn enough that it leaves a raised edge on the outer or inner rim (or both). When this happens, the edge of the pad that enters in contact with the raised edge when you brake will eventually fray and crumble, generating the electrical conductivity that activates the warning light. This is typically intermittent until the pad edge becomes so frayed that it triggers it more frequently: interestingly, I noticed that very light braking tends to trigger it more than stronger, harder braking. 

You can verify this by taking a wheel off (most often one of the front ones) and visually and physically (with your finger) inspecting the rotor, as well as, visually, the pad. If they are in the condition I described, the eventual solution is to replace pads and rotors, though you may still have enough friction material to pass an inspection. 

Finally, a comment about the mileage: 28k is a bit on the early side, but brake wear depends so much on driving style and traffic conditions that it cannot be ruled out: I have seen front pads last 70kmiles and rears as much as 90-100k, and others last as little as 20k.

Good luck and keep us posted.
Stefano


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## invisiblewave (Sep 22, 2008)

How does the edge of the pad crumbling possibly create electrical conductivity in the embedded sensor?


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## Motorista (Oct 28, 2005)

I suspect that it's because the loop is across the width of the pad, so as the crumbled edge comes in contact with the raised edge of the rotor it is enough to close the electrical circuit. This is just my guess but it would explain why it is intermittent.
Stefano


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## invisiblewave (Sep 22, 2008)

Maybe newer ones are different then, because the older ones definitely only have a small contact patch. Unless you're running really awful pads, the edges shouldn't start to disintegrate anyway until they're pretty badly worn, and even then not much. For me, the wear sensors are a secondary thing, eyeballs are better. I don't think I've ever seen the wear indicator come on. Much like TPMS, they're a solution looking for a problem.


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## Victor R (Jan 7, 2010)

See my posts earlier in this thread. My problem was intermittent contact through rusted wires to the sensors, not a problem with the brake pads themselves.

Victor


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