ABS Sensors 4th gen

[wurlycorner]

I presume you can use the 2ws ABS sensors on the 4ws versions, they look identical?

Yep

[EddieMunster]

I presume you can use the 2ws ABS sensors on the 4ws versions, they look identical?

Yep

I've actually bought a near-side sensor, I was going to check it for consistency and then just graft the sensor on to my existing loom (having checked that too) rather than try and force nearside to far side (unless it's an easy job to do).

[wurlycorner]

Don't go messing with the cabling - that is guaranteed to fail. They're not standard power carrying wires, they're low current signal carrying.

Believe me, it's far simpler and more reliable to just swap the cable over from one bracket to the other.

[EddieMunster]

Don't go messing with the cabling - that is guaranteed to fail. They're not standard volt carrying wires, they're signal carrying.
It's far easier swapping the cable over from one bracket to the other.

Roger that!

[EddieMunster]

Don't go messing with the cabling - that is guaranteed to fail. They're not standard power carrying wires, they're low current signal carrying.

Believe me, it's far simpler and more reliable to just swap the cable over from one bracket to the other.

What is odd is that the ABS light will show as soon as you pull away, but the 4WS will be working fine (I've done a static test, i.e. opened the door, hung out and looked at the rear wheels, they were moving to and fro as expected), and then after anything from 10-60 seconds later, the 4WS light will show and the 4WS will stop working.

It's a little odd that both errors say the same thing, but, it's not affected the 4ws initially.

[DanishLuder]

@wurlycorner
Does 5th gen ABS Sensors work for 4th gen models? Do you know?

[wurlycorner]

What is odd is that the ABS light will show as soon as you pull away, but the 4WS will be working fine (I've done a static test, i.e. opened the door, hung out and looked at the rear wheels, they were moving to and fro as expected), and then after anything from 10-60 seconds later, the 4WS light will show and the 4WS will stop working.

It's a little odd that both errors say the same thing, but, it's not affected the 4ws initially.

4WS doesn't lock out straight away - there is no comms between ECU's on the 4th gen, all the ECU's work independently (this pre-dates can-bus automotive electronics).

So basically, the ABS does a static check of its own system on start up and if it identifies a fault component then (or immediately on vehicle starting to move) it will lock out straight away. However at that point, the 4WS doesn't know the ABS module has identified a fault and unless it has identified a fault within its own system, it assumes all is good.
After the vehicle starts moving (plus a pre-determined time-out*) the 4WS ECU will spot that it is getting e.g. lots of steering angle input and a speed sensor input from the front (VSS) but no speed input from the rear wheels and only then will it throw it's own fault and lock out.

*The 4WS has an additional time-out built in, I assume because this is to prevent the 4WS system from incorrectly going into fault mode during e.g. an ABS activation (skid = imbalance in speed sensors) or imbalances in wheel speed during slow speed manoeuvres, wheel spin etc.

[EddieMunster]

Hi

I've had the rear assembly apart today, to do the rear brakes and check the bushes, and I've noticed the following:

1. The offending sensor, driver's side rear, has been interfering with the ABS ring as the ABS ring is very shiny. The shine is recent too, you can see that it's a constant interference as there's no surface marking/road muck on the exposed part of the ring -I've seen less shine in a branch of Pandoras!!! I've only viewed it via the back plate, so I can't see well enough to see if the teeth are all fine, but it definitely looks as though the sensor is hitting the ring.

So:

1. Might the sensor itself be fine, with the poor reading caused by the ABS ring confusing the ABS ECU into thinking that the sensor itself is damaged? On that note, can the ABS ring be changed independently or is it part of an overall hub assembly? Or, do we still assume it's a sensor?
2. Or, do we still assume it's the sensor. I have the replacement sensor, albeit from the opposite, and whilst I could change it for piece of mind, it'd be useful to keep for "just in case" at a later date.

Regards

[indigolemon]

If the sensor has made contact with the ring, the ring will likely be in better shape than the sensor I'd think.

Can you unplug the sensor and measure the resistance across the pins? It should fluctuate as you rotate the hub. If you get infinite resistance (usually shown as '1' on a digital meter) I suggest the sensor is gone.

When fitting a new one, you can shim with thin washers if you think it's also making contact.

[EddieMunster]

When fitting a new one, you can shim with thin washers if you think it's also making contact.

I'm not allowed back under the car until next week, but that'll be my first point of call!

When you say shim, I presume you mean the ABS sensor and not the ring?