[tadaska]

Need to get my car in for an MOT but have a front brake sensor light on. I know brakes are okay. And I don't have time to get all the tools from the loft go get to the sensor. Can it be done from the engine bay? Where does that wire go?

[rasa bmw]

i had a snapped wire on sensor,,,tester showed me,,,advisory issued,,the brakes work fine so assume this is what they do,,did with mine,,naturally i replaced the sensor a week later but passed the mot

[therealdb1]

If it is only a pad wear sensor warning I would argue that it is not an MOT fail because pad thickness is not part of the MOT. Provided it passes the brake function test it is ok. You will no doubt get an advisory for it and quite rightly.

But, if you mean the warning light is for abs or something then it should fail MOT because the brakes are not working correctly.

[tadaska]

The INPA code said front brakes. Might just ask them before booking it in.

Still looking for a way to remove the sensor wire from the engine bay if possible. I think I saw somewhere it goes to some ABS module?

[sirleeofroy]

I'm pretty sure this is in the wheel arch and simply clips in, I might be wrong but you might just be able to remove the wheel and unclip it..... Shame you're nowhere near me as I actually have a spare sensor....

[N5GKP]

Originally Posted by therealdb1

If it is only a pad wear sensor warning I would argue that it is not an MOT fail because pad thickness is not part of the MOT. Provided it passes the brake function test it is ok. You will no doubt get an advisory for it and quite rightly.

But, if you mean the warning light is for abs or something then it should fail MOT because the brakes are not working correctly.

Pad thickness is part of the MOT just an FYI.


You can disconnect the pad wear sensor without too much difficulty. iirc it's the passenger front wheel arch, turn the wheel on full lock and you'll be able to get to the connector - just make sure you disconnect the pad wear sensor and not the wheel speed sensor.

[tadaska]

Originally Posted by N5GKP

Pad thickness is part of the MOT just an FYI.


You can disconnect the pad wear sensor without too much difficulty. iirc it's the passenger front wheel arch, turn the wheel on full lock and you'll be able to get to the connector - just make sure you disconnect the pad wear sensor and not the wheel speed sensor.

Thanks, I'll give it a try. I didn't even think of that.

[therealdb1]

Originally Posted by N5GKP

Pad thickness is part of the MOT just an FYI.

What is the minimum requirement?

Is it just a visual check?

I cannot believe that friction material is measured at MOT otherwise my car should have failed last time round!

[therealdb1]

Originally Posted by N5GKP

You can disconnect the pad wear sensor without too much difficulty. iirc it's the passenger front wheel arch, turn the wheel on full lock and you'll be able to get to the connector - just make sure you disconnect the pad wear sensor and not the wheel speed sensor.

Are you suggesting it will fail with a pad warning light on but if you remove the sensor to turn the light off it will pass?

That's a typical daft Government ruling like most they come up with if that is the case.

[N5GKP]

Originally Posted by therealdb1

What is the minimum requirement?

Is it just a visual check?

I cannot believe that friction material is measured at MOT otherwise my car should have failed last time round!

The minimum requirement is 1.5mm, how the tester decides on that is down to them because measuring pads is a bit of a grey area. You can use a special pad measuring tool, but more often than not they're a pain to get in.

The way I see it, and this applies to a lot of the MOT, is if you're in doubt as to whether it meets the minimum requirements and cannot categorically say it should fail, you should give the benefit of the doubt and pass + advise.

Equally, a vehicle presented with a pad wear warning light on isn't reason for failure anymore, because the minimum limit is 1.5mm, but BMWs pad wear indicators trigger the warning at 3.7mm - so although the MOT manual states it's a major failure, this is referring to a mechanical wear indicator (squeeler) or an optical one (grooves).

The MOT is a nightmare, my current job is as a MOT site auditor, I also teach the class 4&7 MOT course & MOT managers course.

[rasa bmw]

removing pad wear sensor will still give a pad wear light,,ive just said,,mine was snapped,,so just like its removed,so will still light up,,but will not fail mot as ive said

[therealdb1]

Originally Posted by N5GKP

The minimum requirement is 1.5mm, how the tester decides on that is down to them because measuring pads is a bit of a grey area.

Thanks for that, very useful to know.

I write procedural and statutory compliance documents for a living as well as recently being involved in local government (but no more after the farce of the last 3 years!) and I have to say that the most ambiguous and woolly documentation originates from government offices. Some of them make Microsoft Help appear useful!

[tadaska]

Any idea which one is the brake pad sensor?

[tadaska]

From google images it looks like the white one. I had it disconnected hoping to test it with a multimeter but no luck there - the pins are too deep inside that white connector sleeve. I then bent a staple so it's just the right size and pushed it in where the sensor's pins would go hoping that would complete the circuit and fix the problem but it made no difference. I don't know if the staple made no contact or the fault is somewhere higher up the wires or if something has to be reset first before the light goes away.

Any ideas?

I don't mind jacking the car up if needed. I'll just have to wait until Sunday.

[therealdb1]

Originally Posted by tadaska

Any idea which one is the brake pad sensor?

Why don't you just follow the wires?

If you are at the connector box under the wheel arch the wires are only 18" long!

One will go to the abs sensor bolted to the hub and the other should end up somewhere near the brake pads.

If the brake pad wear sensor is shot anyway why not cut through the cable and strip a bit back so that you can twist the conductors together and then the light will go out on your dash if that is what troubles you. Don't forget to wrap some insulating tape around the joined wires though.

Or alternative thought, you could just buy a new wear sensor and fit it Genuine BMW wear sensors are not expensive. Speak to Cotswolds today and you'll have one tomorrow or the day after.

[tadaska]

Originally Posted by therealdb1

Why don't you just follow the wires?

If you are at the connector box under the wheel arch the wires are only 18" long!

One will go to the abs sensor bolted to the hub and the other should end up somewhere near the brake pads.

If the brake pad wear sensor is shot anyway why not cut through the cable and strip a bit back so that you can twist the conductors together and then the light will go out on your dash if that is what troubles you. Don't forget to wrap some insulating tape around the joined wires though.

Or alternative thought, you could just buy a new wear sensor and fit it Genuine BMW wear sensors are not expensive. Speak to Cotswolds today and you'll have one tomorrow or the day after.

Getting a new one is probably the easiest solution, providing the fault lies with the sensor. And if not at least I will know.

[tadaska]

I just fitted the new sensor, didn't fit it properly, unplugged the old and plugged in the new through the gap behind the wheel. Unfortunately nothing changed. The light is still there. Does that mean the fault lies somewhere in the wiring loom?

[N5GKP]

Have you actually reset the service light through the instrument cluster after replacing the sensor? The light doesn't self extinguish

[tadaska]

Originally Posted by N5GKP

Have you actually reset the service light through the instrument cluster after replacing the sensor? The light doesn't self extinguish

I tried it before changing the sensor. I'll try again. Will have to google how to do it again...

[therealdb1]

Suggest you:

Fit the new sensor properly;

Clear the warning light;

Drive the car for a mile or two to confirm all is ok.

If after completing the whole job the warning light returns we can look at alternative issues.

[tadaska]

Replaced the sensor again (through the wheel gap) and did the reset. All good. Going to get the tools down from the loft and do it properly. Want to see what happened to that sensor.

[tadaska]

Turns out the sensor WAS worn down. I'm surprised how quickly that happened. Maybe a year since I put new pads on. And with my low mile docile driving I thought I was good for a few years. There is still what looks like half a pad there but still...

I did a bypass for now. Need to get new pads.