Hello,
I do not own an 03 S type, but what I do own is the Electronic E brake from one.
After reading all the posts about how this unit continuously fails its owners, I (with some trepidation snagged one out of a dead 03 S-Type in a junk yard).

Now after consulting the wiring schematic, I plugged my actuator and module into a car jump starter. And got the no joy result many talk about.

I ran my test leads to the main power wires coming out of the module and going into the actuator motor. What I found perplexed me.

I had positive voltage equal to the input voltage going to both leads.

Now this is a reversing polarity motor. So I should have gotten a positive voltage on one lead, and a negative on the other. So no wonder the motor wouldnt run.

Next I hooked up the motor directly to battery power to test if the motor was seized. Nope it ran like a champ, however, at the end of each stroke, the motor would sound rachetey. So next I pulled the nose cone off of the actuator motor, and found a very small and thinly threaded rod. This rod had stripped the threads off of each end of its length. This no doubt was caused by the module not telling the motor to shut down at the end of its stroke like it should.

The bolt size of this thread that lock your brakes up is WAY TOO SMALL for this type of duty. I dont have an exact size for the rod, but its about 8mm in thickness.

The only hiccup I had on wiring this unit was the schematic showed a green wire coming out of the control module, instead I had a white with red stripe wire in its location.
I am going to further take this actuator motor apart to see if I can get this rod replaced with something beefier. That will fix the actuator, but not the problem with the control unit.

Has anyone come up with anything similar to this problem from the control unit? The circuit card shows no signs or being burnt or worn out in any way. But if this controller has a faulty design it would tell the motor not to stop when it should, stripped the drive threads inside... Which mine obviously has....

Id like some input from owners on this. Maybe some tech info if anyone has some.

Thanks

 

The number of failures seen is actually quite small relative to the size of the fleet. Most common is the gearbox/drive unit losing it's grease and subsequently seizing. If there's a design issue, it might be with not sealing the unit properly or not calling for scheduled re-greasing.

 

Thanks,
Then maybe my unit does not have the A-typical problem(s).

It looks like either the control unit failed or the hall effect sensor at the actuator noses base failed, which caused other problems.

I get positive voltage on both leads to the motor (which shouldnt happen)
The main drive shaft is stripped at its base (the last bit where the controller should pick up (via the sensor) the end of the stroke) But for some reason it didnt and tore through the threads.

I was hoping someone might shine some light on this for me. Since I have read so much about the problem.

Thanks

 

The very common issue is a message saying it's faulty - but actually it's a bad car battery and when that is replaced the EPB is fine.

Fairly uncommon is that the actuator/motor fails and a small number of members here & UK forum have had to replace it. Awkward access!

However, surely more & more will fail as the cars age.

We've also had cases where the (Bowden-type) cables to the calipers are failing to move due to lack of maintenance - and I would expect that could easily be a cause of damage to the actuator.

It seems rare for the module to fail so you were unlucky (or got its wiring wrong or blew it). Sometimes I think the module refuses to drive the motor because the motor is in effect jammed, but bypassing the module "works". (Possibly doing unknown damage by allowing too much current with a tendency to strip gearing etc.)

Maybe the module floats both outputs to the motor when inactive,

BTW, the only green wire I see on the schematic is an input so isn't "coming out" of the module. WR is a mystery.