I spent a nearly a year chasing my tail with EPB issues, I swapped the ECU for a used "good" one, chased wiring, banged my head against a brick wall.

I got to the stage of buying a couple of litres of unleaded and a box of matches, but decided out of desperation to buy a new ECU from the local dealer, cost a few hundred quid but worth every penny.

I uded the petrol in my lawn mower and kept the matches dry for another day :ROFL:

Never saw the issue again, not sure if it re-occurred but mechanico-lee would know!

FWIW and from memory the motor each side is driven by a TRIAC in the ECU, which when too much power is put through them then overheat and die a slow death. As it happens, a failing motor draws enough current to cause this, especially if not replaced quickly. I think some opened up the ECU and replaced the faulty components, I suspect others replace and then out their old "good" ones on ebay :Confused:

Good thoughts. Today I ordered a new connector and 4 repair wires.
Rediclous £42 at TPS - I didn't pay so may not go back and instead just get them online. £1.99 delivered from China for the connector from aliexpress with the wires, seals and pins assembled, but alas with thinner wires so would need to upgrade them. I need 2.5mm2 and 4.0mm2 but these are 1mm2 and 2.5mm2. I can get the correct pins from ebay for about £10 for 10 each size and use my own wire.

Good point about faulty ones on ebay sold as working as they were people's old originals- I did think of that and sought one from a car being broken up rather than a one-off sale.
I did test continuity the lazy way via the resistance of each side's pins for hall sender and motor matching left and right but I hope to be able to make up a test cable with my connectors and pop the 4 pins from the ECU plug and replace them with those of my test lead and try this before working on the loom.
Thank you

Attachment 17756


7D0945527 grommet
1J0919231 flat contact housing, connection piece, servomotor 4 pin X;2;2

2.8 mm female flat terminals
000 979 021 (000979021): 0.5mm wire
000 979 133 (000979133): 1.0mm wire
000 979 225 (000979225): 2.5mm wire x2 xxxxx

4.8 mm female flat terminals
000 979 023 (000979023): 0.5mm wire
000 979 135 (000979135): 1.0mm wire
000 979 227 (000979227): 2.5mm wire
000 979 306 (000979306): 4.0mm wire x2 xxxxxx

If anyone's interested for future reference, they are also the parts needed for adding extra blade fuses to vacant positions on fuseholder.

2.8 mm terminals are for the smaller ATM fuse.
4.8 mm terminals are for the larger ATC fuse.

Snap , do you have an amp meter or inductive amps clamp or multimeter that can manage up to say 30 amps

Snap, you've got a PM +++

High Lee yes, but is doesn't work unless you seperate out a single wire, can't do + & - in the clamp together.


A bit of sun and no snow so I took both calipers off today.
Left and right are not physically interchangeable (I was wrong when I said that earlier) but are electrically identical.
I swapped them over and blocked the piston with a block of wood. The problem stays on the same side so definitely wiring problem.

Attachment 17786

I cut into my previous repair which was still perfect but the damp wire had continued to corrode further along. (black wire syndrome)

Attachment 17790

Attachment 17788

Attachment 17789

Very bad, I cut it back as far as I could and cleaned and de-oxidied with deoxit and scraping with a scalpel. Soldered on new wires and connector, but same errors. I think the wire is too far gone.

Attachment 17787

I have looked at the loom and I can see branches split off to speed sensor, height sensor and EPB. They are all moulded into one tough insulated assembly that converges and disappears as one thicker rubberised cable up behind the rear wheel arch liner.

My options are to install a new partial loom but not sure how it fits, cut existing and splice in a partial used loom or to make another cable - EPB motor plug with 4 wires and wrap it as a loom all the way to EPB module and pop out the existing 4 and insert new ones.
Thinking about it.

Wow, 3 months and a week later, I finally got chance to fit my new home-made partial loom and it works! Phew. Also had to pop out the piston and replace the dust boot as that had ripped somehow (on left and right sides)

Had to remove the rear wheelarch liner so cleaned that all above and behind it with pressure washer. Found the accululator on the air shock was a bit rusty on the seam so put some anti-corrosion wax on it.

A couple of panel clips broke, the part number is 4D0807300

Attachment 18279


Attachment 18280

New cables were insered into gland just behind damper which is next to plastic vent in the side triim of the boot interior and can be reached by hand and pulled - only had to remove navi/TV access panel.
Then routed behind plastic boot slam panel trim and to EPB control unit uner the battery.
When I popped the pins out of the large connector on the EPB ECU, the contact was a different design that those I had bought, so I cut and soldered to the existing wires. (two thick and two very thin for the hall sender)

Did you ever get around to testing an A6 EPB module before diagnosing the wiring fault? A lot of A6 parts (4F0 part numbers) seem to be interchangable with A8 ones. I think this would be more likely to work than a module from the D4 A8.

I've also had a couple of intermittent parking brake faults in recent weeks. It's still working correctly now so I'm hoping it was just due to the cold weather as previously mentioned.

If I ever need to replace the module (or motors) in future then I'll try an A6 one. The 2-pin motors are also much cheaper.

Thanks didn't get wound to getting an A6 module, still trying to sell the 4H one :( If I see a really cheap one I might try it. The 2pin motors are about £30 on aliexpress!

All these problems could have been avoided if 10 years ago, West London Audi had followed Audi repair procedures.
Instead, they nicked off a bit of insulation on all 4 wires to the EPB motor cable presumably to probe with a voltmeter - and put a bit of tape over their damage. This allowed moisture in over the years that rotted the conductors.

Attachment 18285

Old thread I know but just wondering.. so on this note I recently purchased a Passat electric motor for the rear caliper and it was only around £25. It too had only two pins and the connector is physically mounted to the actual motor (as oppose to a wiring loom with the connector on the end of the loom, as is with the A8 D3).

I would be curious to know if I can somehow customise this to retrofit it to my rear caliper. What are the additional 2 wires for on the D3? Does anyone know?

thanks

Maybe someone who can read current flow diagrams can assist. Here is the relevant diagram, and from it I can see that the two heavier wires go to the actual motor. Not sure about the other two.

http://forum.a8parts.co.uk/attachmen...1&d=1562759564