Hi everyone,

 

Today I had a bit of a big job on my Fabia. Changed brake discs front and back, pads front and back, and brake calipers back.

Job went well, took pretty much the whole day but was quite fun! Bled the brakes and it's like new again.

 

.. Only one little issue. I noticed when changing the front pads, that the new pads did not have that "cut out" to place the brake pad sensor in. Not that I really cared though, I always check my pads manually so I don't really need it. Figured I'd just take the sensor cable from the connector since I couldn't put it in the new pads anyway.

All good but now when I start the car I have a "Brake pad warning". Damn it, I thought it would work to just remove the connector. Perhaps the sensor wants to have the sensor in a closed loop to give thumbs up? I figured that's the case so I put the connector back, then cut the cable (the part that goes into the pad) and twisted the two wires together to close the loop.

 

Thought I was smart, went into the car and was expecting the warning to turn off. Nope - still warning.

 

Now out of ideas. Basically what I want is to just "disable" the sensor or reset it somehow so it doesn't warn - since I don't really need the warning anyway.

 

Anyone have any  ideas what I could do to overcome this issue?

 

Thanks

 

Vol

I'm surprised that if you can back the "flying lead" from the old pad twist the wires together and solder them and then seal in heat shrink tubing - preferably the type with heat activated adhesive/sealant, that the brake warning light did not go off.

 

If you have VCDS, you should be able to find where the "brake wear sensor fitted " coding is and switch it off, I seem to remember needing to switch my on in my 2000 VW Passat 4Motion as it came new with that feature not enabled!

 

Edit:- Fords, at least from back in the 1980's used a 3 wire system, so leaving the cable unplugged would force a flashing light, but any VW Group ones I've seen from 2000 > 2019 only have a 2 wire system. 

Edited 10 August, 20241 yr by rum4mo

It will be in the instrument cluster coding, I believe. Module 17.

 

3 minutes ago, rum4mo said:

I'm surprised that if you can back the "flying lead" from the old pad twist the wires together and solder them and then seal in heat shrink tubing - preferably the type with heat activated adhesive/sealant, that the brake warning light did not go off.

 

If you have VCDS, you should be able to find where the "brake wear sensor fitted " coding is and switch it off, I seem to remember needing to switch my on in my 2000 VW Passat 4Motion as it came new with that feature not enabled!

Yeah me too, perhaps the connector is not working properly and disconnecting it "triggered" the issue?

Maybe I can cut the wires even further off, before the male connector and wire the two wires together there to rule out the actual connector?

 

Vol

Just now, Breezy_Pete said:

It will be in the instrument cluster coding, I believe. Module 17.

 

 

What exactly does this mean? Sorry but this was new language to me Mind elaborating?

 

Vol

I'd always think that it would be a better plan to keep the car wiring as it is and modify the lead out to the pad, so that this can be reversed in the future maybe by the next owner.

 

It sounds like you will not be able to code this out yourself if what Breezy Pete wrote confused you, maybe get a workshop to do that for you - if it is legal to do that in your country.

If two then its probably a normally closed circuit where the circuit is broken when the pad wears low and wears through the cable.

 

What you describe sounds more like a 2 pair system, one pair normally closed to make sure the connector is in place and the pads have the sensor and a normally open pair buried in the pad which will make a closed contact when the pad wears and the current runs through the disc between them.

5 minutes ago, J.R. said:

If two then its probably a normally closed circuit where the circuit is broken when the pad wears low and wears through the cable.

 

What you describe sounds more like a 2 pair system, one pair normally closed to make sure the connector is in place and the pads have the sensor and a normally open pair buried in the pad which will make a closed contact when the pad wears and the current runs through the disc between them.

But wouldn't there be more than two wires inside the cable then? I mean, not that I'm an expert - but if two wires are in the cable, it's either going to be a warning when the loop is "broken" and current is not running through - OR the warning triggers when the loop is closed and the current is running through.

 

Since I've tried the connector off completely that would mean the loop was "open" and current could not run through. That gave a warning - so i tried closing the loop, hardwiring the two wires together - but that still gives a warning.

 

Very confusing

 

Vol

Did you try driving the car during any of this testing? Sometimes you just need to start up and set off down the road before these systems reset themselves after a fault is rectified. 

 

Maybe leave the sensor attached and tape it up then out of the way?

 

The wiring must be getting a reading from the sensor when its intact to let the system know its present which changes when it meets the disc.

56 minutes ago, Breezy_Pete said:

Did you try driving the car during any of this testing? Sometimes you just need to start up and set off down the road before these systems reset themselves after a fault is rectified. 

 

 

Nope, actually didn't.. I'll try that tomorrow!

I have not seen a separate sensor, simply a wire loop embedded in the brake pad during manufacture, I'm pleased that my current poverty spec vehicle is devoid of this sort of nonsense.

1 hour ago, volatyle said:

But wouldn't there be more than two wires inside the cable then?

 

2 hours ago, J.R. said:

What you describe sounds more like a 2 pair system

 

2 pair = 4 wires.

I would have thought a simple wear detector would be just one wire which detected a return to earth when reached.

 

So two wires suggests one of them is to detect the feature is present?

 

 

Sensors are usually in the new pads i have not experienced putting sensors from old pads in the new ones

 

29 minutes ago, J.R. said:

 

 

2 pair = 4 wires.

 

Exactly, and I have only 2 wires in total in my cable - so what are the options besides either connecting them together or having them separate?

2 hours ago, rum4mo said:

I'd always think that it would be a better plan to keep the car wiring as it is and modify the lead out to the pad, so that this can be reversed in the future maybe by the next owner.

 

It sounds like you will not be able to code this out yourself if what Breezy Pete wrote confused you, maybe get a workshop to do that for you - if it is legal to do that in your country.

 

By coding, do you mean connecting like a ODB2 reader and clearing it from there? I do have one of those bluetooth OBD2 readers that I could connect if that can make a difference.

42 minutes ago, Stonekeeper said:

I would have thought a simple wear detector would be just one wire which detected a return to earth when reached.

 

So two wires suggests one of them is to detect the feature is present?

 

 

Sensors are usually in the new pads i have not experienced putting sensors from old pads in the new ones

 

 

It's normally a thin wire in the pad material that goes open circuit when it wears away. Either fit the right pads, or put a loop of wire in the plug if you're not bothered about such things. 

34 minutes ago, StevesTruck said:

 

It's normally a thin wire in the pad material that goes open circuit when it wears away. Either fit the right pads, or put a loop of wire in the plug if you're not bothered about such things. 

 

Yeah, it's just that looping the two wires still gives the error. That's what so mind boggling about this..

 

Vol

Every VAG I have owned has been 2 wires, closed CCT for good, open CCT for warning.

 

Apart from when you damage the cabling, which can easily happen if somebody has been a bit rough when changing out suspension components etc. and caught the cable.

If there was no wear warning light on prior to changing the pad, would it be possible to plug the old pads back in if you still have them to see what happens. Don’t have this system so not sure. Just a thought…

I wonder if I should find a place "higher up" on the other side of the cable, (where it starts) and try hardwiring there. Perhaps something broke in the cable when I messed around so hardwiring them at the very bottom still doesn't close the loop?

I assume the cable goes from the brake pad to somewhere around the engine or electronic box?

 

Vol

Follow up;

As I suspected the connector probably had broken too while changing the brakes. (which made this a bit hard to troubleshoot) but I now cut the cable "above" the connector and did the very same hardwiring there in stead, warning gone.

Phew, that was a tough one!

 

Thanks for all the support.

 

Vol

There was another possibility to the mind boggling, its not relevant now you have found the fault but it may help for a future enigma.

 

It was a normally closed circuit like most safety circuits, its one that is at risk of someone disabling it in exactly the same way as you had, to prevent this the manufacturer could have fitted an end if line resistor EOL in the brake pad instead of the (zero resistance) loop of wire, the controller would be looking for a volt drop commensurate with the say 2.2k ohm resistor to decide the system is normal, the warning light would be illuminated for either of 2 conditions, if it goes open circuit through pad wear or closed circuit through it being shunted as you have.

 

Airbags etc usually have this type of security. It is/was also common on Fire Alarm and Burglar Alarm systems.

I had considered that option as well. We used that system on safety-related interlocks.

On 11/08/2024 at 12:28, J.R. said:

There was another possibility to the mind boggling, its not relevant now you have found the fault but it may help for a future enigma.

 

It was a normally closed circuit like most safety circuits, its one that is at risk of someone disabling it in exactly the same way as you had, to prevent this the manufacturer could have fitted an end if line resistor EOL in the brake pad instead of the (zero resistance) loop of wire, the controller would be looking for a volt drop commensurate with the say 2.2k ohm resistor to decide the system is normal, the warning light would be illuminated for either of 2 conditions, if it goes open circuit through pad wear or closed circuit through it being shunted as you have.

 

Airbags etc usually have this type of security. It is/was also common on Fire Alarm and Burglar Alarm systems.

 

We use a similar sytem on industrial fire systems where we have 1 resistor is series and 1 in parallel locally on a NO open contact so the system can distinguish between an open circuit/dead short and a genuine alarm to prevent false activations which is quite important when you are potentially soaking large generators and transformers in water.

 

2K2  and 4K7 ohms EOL and shunt resistors n'est ce pas?

 

I still have hundreds of them!

 

Or maybe those were the values of one intruder alarm manufacturer who used the same system, twas a long time ago!