ABS Issue (Brakes locking up) - Not common fault

[Leemarty6]

So let’s start by saying I’ve just bought my E86 coupe, since owner ship it’s spent more time in the garage then in my hands.

After clutch rattle on return home I change the clutch replaced, as I intent to keep this car for some time with some track use. Took it on the chin

Some time after driving speedy and coming to a sharp brake. The back wheels lock up. I mean snaking down the road with smoke out the back, down to 0 and then brakes release. After releasing this it happeneds on any hard brake progressing or sharp.

Now after this happening coming up to a roundabout I took it straight to my garage.

Diagnosis shows:

5E5D Brake Fluid Level
5E1EH/24094 Undocumented Code
5E14 DSC No message Engine Management
5E16 DSC No message Engine Management

All codes will clear

No lights on the dash at all.

Now I was advised by the garage to send to ECU testing which I did, I hoped for <300 and be on my way. Unfortunately I was not that lucky. I’m now a little lost at what to do and have dropped the car to BMW Sytner for a diagnosis. They said they couldn’t get the car to do it on road test - I said they wasn’t braking hard enough as it happened every time without fail.

Does anyone have any comments or advise before I fork out for a replacement ABS module used/old is going to cost an arm and a leg and my right ear.

 

[Jakg]

In advance, I'm not a mechanic. But I have had to do a lot of ABS fault finding on my MG ZT, which uses a lot of the E46-era BMW technology.

Were you braking hard or not? I.E. was the pedal command enough to lock the wheels, and you were expecting the ABS system to prevent this?

Or are you saying that the brakes simply came on full power and locked up the rears, without you really trying?

Part of a modern ABS system is EBD (electronic brakeforce distribution), which ensures braking is distributed fairly. Without this you might be surprised by what locks up first - on my ZT, without the ABS system the rears would lock up under moderate-hard braking.

On my ZT, removing the ABS fuse would disable the system to allow you to test it without it.

 

[Leemarty6]

Were you braking hard or not? I.E. was the pedal command enough to lock the wheels, and you were expecting the ABS system to prevent this?

Yes I would say it’s on hard braking. The ABS should probably kick in.. it should pulsate the brakes automatically but it seems to be locking ON. Which is not good

 

[Scooba_Steve]

Try a fluid change and a proper pressure bleed activating the ABS module (INPA can do this). If the valves are sticking I'd expect it to show, though it could be an ABS sensor.

 

[ph001]

I don’t even think the ABS is capable of doing that, it can only decrease hydraulic pressure not increase it...that is a mechanical operation due to the master brake servo and vacuum. The DSC system can apply brakes via the ABS pump I suppose but again, I would expect specific codes for wheel speed sensor AND it would have to be in combination with throttle input, yaw or lateral acceleration. I suppose an easy thing to do would be to disable the DSC completely by pressing and holding the button. That may eliminate things.

Failing that, I would be getting the rear brake calipers refurbished as it sounds more like a sticking piston or perhaps the slide pins. It is a little strange how they unlock once you stop though.

A fault with the ABS module ALWAYS brings on a distinct set of warning lights on the dash with these cars along with some very typical fault codes.

 

[Leemarty6]

I don’t even think the ABS is capable of doing that, it can only decrease hydraulic pressure not increase it...that is a mechanical operation due to the master brake servo and vacuum.

My thought was that the fault in the ABS is that the pressure is not being released hence why it is sticking/locking on. My garage said that one the wheel sensors read 0 they unlock..

I collect the car tomorrow from BMW (Who could no find the route of the problem , they need the codes to be on the car to give them guidance on further testing) so been told to run some miles on it and take it back in a couple weeks.

Lucky he said he’s not going to charge me a penny because tbh they haven’t actually done anything, he suggested a rear end replacment brakes, callipers etc did not suggest ABS module once unlike my local garage (Who I trust). They confirmed no visible faults with individual speed senors or steering wheel angle etc. Although the car pulls to the left slightly

I will try describing the DSC tomorrow and seeing if symptoms are still there.

Need to get this traveled have a stack of AD08Rs ready to go on

 

[MACK]

This sounds a lot like the Dynamic Brake Control but with a failure of the ABS system to prevent lock up

Cut and paste from the manual

"Dynamic Brake Control DBC
If you step on the brake rapidly, this system
automatically produces maximum braking
force boost and thus helps to achieve the
shortest possible braking distance during
panic stops. All of the benefits of the ABS
system are exploited under these circumstances.
Do not reduce the pressure on the brake
pedal for the duration of the brake application.
When the brake pedal is released, the
DBC is deactivated."

 

[Leemarty6]

This sounds a lot like the Dynamic Brake Control but with a failure of the ABS system to prevent lock up

Cut and paste from the manual

"Dynamic Brake Control DBC
If you step on the brake rapidly, this system
automatically produces maximum braking
force boost and thus helps to achieve the
shortest possible braking distance during
panic stops. All of the benefits of the ABS
system are exploited under these circumstances.
Do not reduce the pressure on the brake
pedal for the duration of the brake application.
When the brake pedal is released, the
DBC is deactivated."

A quick read suggested this is the issue as the car unlocks the back wheels when the car is stopped at 0 mph..

The question is what’s causing the ABS issue, my garage recommended the ABS module ofc. He’s a good garage and cannot point a finger at any other component that could cause such an issue. Which lies my problem. I don’t want to trial and error with the module at this stage as I need to be certain it is, before forming out. As there not cheap

But thanks I will relay this info to the garages including BMW who are trying to figure it out for me

 

[brillomaster]

Must say, though i cant help cure the problem, i have experienced the symptoms, and its not pretty. Had an old 2000ish 328i as a track car, foolishly went out for a session with an abs fault showing. I thought no worries, dry day with grippy tyres, very unlikely to lock up.

There i was, barrelling down the back straight at bedford at about 100, hit the brakes late and the rears just locked up. With little time to react, the rear jinked left, then did a full 720 back the other way. Fortunately managed to slide to a stop still on track, but it was a massive brown flag moment that would have ended very badly had there been a car in front of us.

The rear tyres had a flat spot and both needed to be replaced... but lesson learnt, get your braking system sorted before going on track!

 

[MACK]

This sounds a lot like the Dynamic Brake Control but with a failure of the ABS system to prevent lock up

Cut and paste from the manual

"Dynamic Brake Control DBC
If you step on the brake rapidly, this system
automatically produces maximum braking
force boost and thus helps to achieve the
shortest possible braking distance during
panic stops. All of the benefits of the ABS
system are exploited under these circumstances.
Do not reduce the pressure on the brake
pedal for the duration of the brake application.
When the brake pedal is released, the
DBC is deactivated."

A quick read suggested this is the issue as the car unlocks the back wheels when the car is stopped at 0 mph..

The question is what’s causing the ABS issue, my garage recommended the ABS module ofc. He’s a good garage and cannot point a finger at any other component that could cause such an issue. Which lies my problem. I don’t want to trial and error with the module at this stage as I need to be certain it is, before forming out. As there not cheap

But thanks I will relay this info to the garages including BMW who are trying to figure it out for me

Not 100% sure but seeing as the ABS pump/module controls both the ABS and the DBC logically you would think the fault really has to lye there.

 

[Jakg]

This sounds a lot like the Dynamic Brake Control but with a failure of the ABS system to prevent lock up

Cut and paste from the manual

"Dynamic Brake Control DBC
If you step on the brake rapidly, this system
automatically produces maximum braking
force boost and thus helps to achieve the
shortest possible braking distance during
panic stops. All of the benefits of the ABS
system are exploited under these circumstances.
Do not reduce the pressure on the brake
pedal for the duration of the brake application.
When the brake pedal is released, the
DBC is deactivated."

I thought only the Z4M had this?

 

[MACK]

This sounds a lot like the Dynamic Brake Control but with a failure of the ABS system to prevent lock up

Cut and paste from the manual

"Dynamic Brake Control DBC
If you step on the brake rapidly, this system
automatically produces maximum braking
force boost and thus helps to achieve the
shortest possible braking distance during
panic stops. All of the benefits of the ABS
system are exploited under these circumstances.
Do not reduce the pressure on the brake
pedal for the duration of the brake application.
When the brake pedal is released, the
DBC is deactivated."

I thought only the Z4M had this?

It's in the 3.0i handbook so you've got to assume they have it and probably the 2.0, 2.2 and 2.5 aswell

 

[buzyg]

Probably nothing similar, but. When I first got my Mondeo Si 24v . The first time I hit the brakes hard the rear locked up. Dusty bumpy country lane. A few days later braking fairly hard, but nothing daft approaching the Saltash tunnel down the hill into the round about. Locked up again fishtailed twice before I gathered it up. Bit of Pooh may have come out.

Any way, staight to the garage this time. bent rear wishbone. My point being, nothing to do with the braking system.

 

[Leemarty6]

So I bought a used abs from a French supplier £800.
Fitted programmed and now the DSC won’t calibrate. Now it’s getting pricey..

I’m looking at a new ABS module and pump from BMW for just shy of 2K with a 7.5% discount. Must return the one from my car to qualify.

All I can do is hope now that this resolved the issue as I’m literally throwing money at it.

If anyone’s got any suggestions will be appreciated!

My garage indicated that no physical component would lock the brakes on, so it must be an ABS fault

 

[wonkydonkey]

If you're looking to replace your ABS module, I'd look into having your original one reconditioned rather than buying new from BMW.

 

[wonkydonkey]

Example of repair service: https://www.ecutesting.com/product-catalogue/bmw/z4/abs-pump-ecumodule-combined/amc916203/

 

[andre.zammit]

So I bought a used abs from a French supplier £800.
Fitted programmed and now the DSC won’t calibrate. Now it’s getting pricey..

I’m looking at a new ABS module and pump from BMW for just shy of 2K with a 7.5% discount. Must return the one from my car to qualify.

All I can do is hope now that this resolved the issue as I’m literally throwing money at it.

If anyone’s got any suggestions will be appreciated!

My garage indicated that no physical component would lock the brakes on, so it must be an ABS fault

Hi, I have the exact same issue with my Z4. Where you able to fix this issue?

I'm tempted to send my ABS module in for a rebuild but as there are not fault codes reported from it I'm not sure this is the way to go.

 

[Leemarty6]

So I bought a used abs from a French supplier £800.
Fitted programmed and now the DSC won’t calibrate. Now it’s getting pricey..

I’m looking at a new ABS module and pump from BMW for just shy of 2K with a 7.5% discount. Must return the one from my car to qualify.

All I can do is hope now that this resolved the issue as I’m literally throwing money at it.

If anyone’s got any suggestions will be appreciated!

My garage indicated that no physical component would lock the brakes on, so it must be an ABS fault

Hi, I have the exact same issue with my Z4. Where you able to fix this issue?

I'm tempted to send my ABS module in for a rebuild but as there are not fault codes reported from it I'm not sure this is the way to go.

Had this resolved in the end! The ABS module has been removed previously and someone installed the connections in the wrong order! so the front was the back and visa versa cost me a fortune to get this figured out and the car now has a brand new ABS module...

 

[andre.zammit]

Glad to hear that! (apart from the costing you a fortune part)

I just sent mine for repair so hopefully I won't need to go through all the hassle of coding a new one.

At least reading your reply gave me a bit of encouragement that the ABS module seems to be the culprit.

 

[andre.zammit]

Had this resolved in the end! The ABS module has been removed previously and someone installed the connections in the wrong order! so the front was the back and visa versa cost me a fortune to get this figured out and the car now has a brand new ABS module...

Hi again, so the ECU Testing path didn't work for me either. They said that my unit couldn't be fixed (and it suffered transit damage as well).

When you tried the used unit and couldn't code it, do you remember what the issue was? I'm assuming the inverted connections problem was on the new unit.