Strange ABS problem

[Roger Chatfield 0]

I've got a strange ABS problem, when cold on startup the ABS light comes on and doesn't go off, however if I drive for a bit and its all warmed up and I re-start the light goes out as per normal.... strange..

 

Anyone had something similar??

 

Any advice on how to fault find this would be great..

 

Many thanks

 

Rog.

[Jon_vr6 1]

Youll need to Vagcom it to be sure but usually the cause is the valves in the ABS pump become clogged and flag up and inlet valve error on vagcom. A quick fix might be to do a brake fluid flush with new fluid but cant guarantee that will work but might be worth a try as after that your prob looking to either change the abs ecu for a known working one as it might have water damage and/or change the abs pump for a known working one

[vw rule 19]

I would change your brake fluid first and go from there,

the fluid should be changed every 2 to 3 years,

as it absorbs moisture.

 

Or could be a faulty hub speed sensor,

some times the plastic housing of the sensor can become brittle,

coursing small cracks and so letting damp in to it,

which can bring the ABS warning switch / light on,

then once the hub has warmed up from the heat generated from the brakes,

it can switch the ABS warning light off.

 

The issue regarding the moisture with in the brake fluid,

is basically brake fluid is just hydraulic oil,

and the ABS pump can't really compress i.e pump the fluid around the system efficiently,

if it's not of the right consistency because it can course low pressure in the ABS pump,

when this happens it can bring on the ABS warning switch / light.

 

I think there's a sensor in the ABS pump unit.

The ABS warning light acts as a switch as well,

so if the ABS pump pressure is too low then the warning light comes on,

and so the complete system can shut down.

 

The ABS warning light should come on once the engine starts,

and will stay on for 8 to 30 seconds as it's checking for any faults including pressure.

The light can just stay illuminated for the 8 seconds or so,

or it can flicker slightly for the 8 seconds or so,

until the system has fully checked it's self.

 

If you've got the VWCOM on your laptop,

you can check for any fault codes, if there are any stored of course.

 

Plus when the ABS pumps are warn they can bring on the ABS warning light for much longer.

 

 

But Like I say I would first of all change your brake fluid for new,

(DOT 4) Brake fluid is the normal grade to use on all / most road cars.

 

Hope this helps.

 

Si

[Roger Chatfield 0]

Cheers for the reply mate, where abouts is the ebs ecu?? I've been sorting out some wiring and wonder if I have disturbed something.

 

Rog.

[Jon_vr6 1]

Cheers for the reply mate, where abouts is the ebs ecu?? I've been sorting out some wiring and wonder if I have disturbed something.

 

Rog.

 

Passenger side left hand side undertray theres a kick plate to the left its under that

[seanl82 23]

It's unlikely the plug has pulled out unless it's been fudged in the past Rob. The plug pivots into the ECU and is held in place by a metal clamp. Sounds like a duff sensor to me which is pretty common and easy to replace.

 

Here is a guide I did on my old mk3 Golf, same principle different platform.

 

http://www.golfgtiforum.co.uk/index.php?topic=204972.0

[Roger Chatfield 0]

I had a PM from Andy (CazzaVR) earlier saying he had a problem with the abs light during the summer, he found the alarm siren was touching the top of the abs unit so moved it, he also cleaned up the plug and the problem went away.

 

Anyway, I noticed that the siren had again slipped down and was touching the abs, so I've moved it, also unplugged and replugged the abs whilst I had the battery disconnected...well guess what, abs light is now working as it should.. :) gotta love having the previous owner keeping an eye on you, many thanks Andy.

 

Rog.

[clumpy1 11]

Good result Cazza is a good guy you were lucky you bought his car mate.

[Dox 23]

Take it out somewhere quiet and make the abs work to exercise the inlet / outlet valves with some heavy braking whilst the light remains off, then change the fluid. What happens to anything mechanical that doesn't get used? it corrodes / gets sticky and wont move when you need it too.

 

My sorned vr6 had the light on permanently with the valve faults, I've changed the fluid, wedged the pedal down for a while and its now intermittent, once its legal to do so I'll make sure the abs pump is exercised on a regular basis. I have a spare pump if its needed

 

First bleed is on the right..... On the left is the flush after

 

[Roger Chatfield 0]

Bad news, abs light is back on, think I'll change the fluid next.

 

Rog.

[CazzaVR 0]

:(

[Roger Chatfield 0]

Light on again this morning, dropped my kids at school (5min drive) and did a restart... light goes out.... strange.... I'm thinking electrical but am open to ideas.

 

Rog.

[Dox 23]

It needs scanning for codes

[rickdonald 10]

I had this exact same problem mate, and so did a friend of mine. He took his to a mechanic who said it was a crack on the circuit board in the ABS module. Caused by the heat in the engine bay and it constantly heating up and cooling down with the drive cycles.

That same heat (when the car is warmed up) expands the circuit board, makes the contact where it is cracked and so the light goes off if you restart.

 

It made sense to me anyway, so much so that I bought a second hand ABS pump module and swap it out…….. it didn’t work straight away, but then I tried bleeding the whole system (cracking off each caliper bleed nipple in turn, and then the two bleed nipples on the ABS module) and using one of those easy bleed things, and it’s been fine since. Every now and again it throws a wobbler, but 99 out of 100 times its fine!

 

I also remember scanning mine and getting a couple of codes, can’t remember them off the top of my head though, will look if I noted them down anywhere when I get home.

 

Maybe try bleeding the system out fully, and replacing the brake fluid while you’re at it. Then if it’s still causing problems, and you fancy swapping the ABS module, then I still have my old one in the shed, and another spare one I got off a mate who was breaking a car (just in-case I had more problems). If you are willing to pay postage (they are pretty bulky)and a couple of quid, then I will send them across to you. I can’t guarantee them 100% though as they have sat in the shed for the last year or so.

 

Will try and get them codes anyway!

[Roger Chatfield 0]

It needs scanning for codes

 

Little update, Sean has kindly lent me his VAGCOM, here is the ABS code.

 

 

So, what's my next move?? I take it the supply valve is internal to the abs unit, is it possible to repair? should I try a fluid change first?

 

Forgot to say, the supply voltage problem has cleared, it's just the valve code that remains.

 

Many thanks

 

Rog.

[dr_mat 0]

Correct, the valve mentioned is internal and cannot be repaired.

Pick up a used one - the modules are actually extremely reliable so the odds of getting a duff one are small.

[agb1980 10]

Little update, Sean has kindly lent me his VAGCOM, here is the ABS code.

 

 

So, what's my next move?? I take it the supply valve is internal to the abs unit, is it possible to repair? should I try a fluid change first?

 

Forgot to say, the supply voltage problem has cleared, it's just the valve code that remains.

 

Many thanks

 

Rog.

 

Hi Rog, did you get this solved? - i've got the same 2 fault codes. I'm getting a replacement pump fitted this week but not sure if this will fix the supply voltage issue...

 

Cheers

Andy

[dr_mat 0]

Supply voltage gets recorded any time you disconnect the battery. Or if you have a really bad connection on the top of the ABS ECU (they can get damp and corrode sometimes).

[Jon_vr6 1]

It can also be the relays behind glovebox that causes supply fault

[iceviolet 0]

It can also be the relays behind glovebox that causes supply fault

 

Interesting, are theses the three relays and a fuse behind the glovebox? wondered what they were for.

 

Do you reckon they could cause the code:

01276-ABS Hydraulic Pump (V64) 16-00 Signal Outside Specification.??

 

Had this code a while and I have just replaced the pump unit and the ECU today! I'm still getting the exact same code.

It brings on the ABS light at about 15mph.

[Roger Chatfield 0]

Hi Rog, did you get this solved? - i've got the same 2 fault codes. I'm getting a replacement pump fitted this week but not sure if this will fix the supply voltage issue...

 

Cheers

Andy

 

Not yet mate, I've got a replacement pump but just need to fit it, be interested to see how you get on with yours.

 

I wouldn't worry to much about the supply problem code, I cleared mine and it stayed away until a disconnected my battery again, like the others have said it always pops up when power has been removed.

 

Rog.

[agb1980 10]

Not yet mate, I've got a replacement pump but just need to fit it, be interested to see how you get on with yours.

 

I wouldn't worry to much about the supply problem code, I cleared mine and it stayed away until a disconnected my battery again, like the others have said it always pops up when power has been removed.

 

Rog.

 

hmmm, well i'll see what happens when the new pumps in- ive cleared the fault codes and the supply voltage one keeps coming back. Maybe will need new relays. Will let u know how i get on

[robrado974 1]

Hope you get this sorted Rog , i have a spare ecu should you need it .

Rob

[agb1980 10]

hmmm, well i'll see what happens when the new pumps in- ive cleared the fault codes and the supply voltage one keeps coming back. Maybe will need new relays. Will let u know how i get on

 

Hi Rog, had new pump fitted today but still have exactly same fault code so next stop is the ecu...

[agb1980 10]

Hi Rog, did you get to the bottom of your ABS gremlins?