Technical ABS Wiring Harness

[ernibv]

Hello all !
I'm looking for a bit of help accessing the ABS harness behind the seats. Or is it behind the rear panel in the trunk? I have to replace the right-rear sensor.
Before I tear into this, any suggestions about how to do this nicely ?
grtz
Eric

 

[Wiltshire Chris]

You can disconnect them from underneath. Below is a picture taken after I'd disconnected them when I dropped my rear axle last winter:

It's also covered in the service manual:

That just leaves the problem of removing the sensor! I followed this guide https://www.fiatforum.com/threads/removing-rear-abs-sensors.149818/ but couldn't get mine to move. As they didn't need replacing I just cleaned and painted around them. If yours need replacing then you can use more force than I did.

Good luck!

 

[ernibv]

Thanks Chris. My sensors are on long cables that go up through the floor before they join forces behind the seat. That's why I'm looking for info about disassembly of the rear area.
If it's too complicated I'll cut the wires under the car and solder the new one in.
As for removal, I destroyed one sensor trying to remove it when replacing the trailing-arm.
The second one popped out easily with a sharp hammer-tap.
grtz
Eric

 

[Simple Simon]

Hi. How did you get on with the sensor wiring? Ive got exactly the same issue. I broke the sensor trying to change the arm, got a replacement sensor but cant find the connector above the floor.

 

[ernibv]

Hi. How did you get on with the sensor wiring? Ive got exactly the same issue. I broke the sensor trying to change the arm, got a replacement sensor but cant find the connector above the floor.

Sorry Simon. I only just saw this message. I cut the wires but did not solder them. Instead I left long tails and used a Western Union splice.
Between the wheel and the wall where they disappear is a molded plastic piece bolted to the chassis to keep it all tight and out of the way. This is a good area to do your work use 2 layers of heat-shrink tubing. Don't forget to put it on before you splice the wires . Then push the splice back up into plastic.
You will need to re-set the computer to confirm the repair. I'm a bit of a nerd, so I tested everything before putting it back in place. The wheel does not need to turn. The computer just wants to read the resistance to turn out the light.
Hope this helps.
ER

 

[Wiltshire Chris]

Thanks for your explanation. I'm a bit confused as isn't the moulded plastic piece you mention the actual connector? They unclip from the chassis and then unplug? I'm interested to see if they are different from mine. I'll try to get some better photos of mine for comparison...

 

[Wiltshire Chris]

So here's my ABS connector just before the cable goes through the wall, photographed from underneath the car just forward of the rear wheel:

Unclipped:

and disconnected:

Are these parts not present on your vehicles at all? If you got replacement ABS sensors did they come without a connector on the end that looks like the one in the photo?
I'm wondering if this is a difference due to changes in the system over time. My car is a late 1998 model so I'd be interested in when your cars are from.

 

[ernibv]

Thanks for your explanation. I'm a bit confused as isn't the moulded plastic piece you mention the actual connector? They unclip from the chassis and then unplug? I'm interested to see if they are different from mine. I'll try to get some better photos of mine for comparison...

There are 2 systems: 1 with a short cable and a visible connector; and 1 with a long cable where the connector is inside the rear of the car and nearly impossible to access. The long cable is the 1 that needs to be cut and spliced if you don't want to dismantle the whole car .
If you look at the rear speed sensor under the car, it goes for about 20 centimeters and then feeds into a plastic channel bolted on the underside of the trailing-arm. This channel is about 25 centimeters long and the sensor cable just presses into it for protection before coming out the back end toward the connector or wall. If I remember correctly it is fastened with a 10mm bolt.
grtz
ER

 

[ernibv]

So here's my ABS connector just before the cable goes through the wall, photographed from underneath the car just forward of the rear wheel:
View attachment 416543
Unclipped:
View attachment 416544
and disconnected:
View attachment 416545
Are these parts not present on your vehicles at all? If you got replacement ABS sensors did they come without a connector on the end that looks like the one in the photo?
I'm wondering if this is a difference due to changes in the system over time. My car is a late 1998 model so I'd be interested in when your cars are from.

My car is a 2001 with a long cable and no visible connector. If you follow your cable to the rear wheel it passes through a plastic channel that holds it up and out of the way. This would be the same regardless of the model.
grtz
ER

 

[ernibv]

Looks like this. Number 7

 

[Wiltshire Chris]

Thank you for explaining that. Yes my 1998 car has the plastic channel on the trailing arm as well. That seems a bad decision (for us) by Fiat to move where the connector lives as the older version is a lot easier to replace! The newer system makes it harder to drop the whole axle out of the car (as I did last year) as disocnnecting the sensors is much harder.
Looking on ePer the ABS sensors were changed in May 1999 so that would match with the the dates of our two cars.
I think your splicing and heat shrink is a good idea to avoid taking the car to pieces.

 

[Wiltshire Chris]

Looks like this. Number 7

OK and on that same diagram I have part 9 - clip which was discontinued in May 1999. This clip is the one in the pictures above that holds the connector in place on the car. So, I guess on your car the ABS cable just goes straight from the trailing arm through the hole and into the car.
This is what my trailing arm looks like before going back in the car,

Thanks for helping solve that mystery for me.

 

[ernibv]

OK and on that same diagram I have part 9 - clip which was discontinued in May 1999. This clip is the one in the pictures above that holds the connector in place on the car. So, I guess on your car the ABS cable just goes straight from the trailing arm through the hole and into the car.
This is what my trailing arm looks like before going back in the car,
View attachment 416547
Thanks for helping solve that mystery for me.

Yes. You have the white plug. Ambitious project grtz ER

 

[ernibv]

Thank you for explaining that. Yes my 1998 car has the plastic channel on the trailing arm as well. That seems a bad decision (for us) by Fiat to move where the connector lives as the older version is a lot easier to replace! The newer system makes it harder to drop the whole axle out of the car (as I did last year) as disocnnecting the sensors is much harder.
Looking on ePer the ABS sensors were changed in May 1999 so that would match with the the dates of our two cars.
I think your splicing and heat shrink is a good idea to avoid taking the car to pieces.

The "un-official" reason for the change is that the Italians can't make a waterproof connector

 

[Simple Simon]

Sorry Simon. I only just saw this message. I cut the wires but did not solder them. Instead I left long tails and used a Western Union splice.
Between the wheel and the wall where they disappear is a molded plastic piece bolted to the chassis to keep it all tight and out of the way. This is a good area to do your work use 2 layers of heat-shrink tubing. Don't forget to put it on before you splice the wires . Then push the splice back up into plastic.
You will need to re-set the computer to confirm the repair. I'm a bit of a nerd, so I tested everything before putting it back in place. The wheel does not need to turn. The computer just wants to read the resistance to turn out the light.
Hope this helps.
ER

So after stripping out the seats, sill trims, pillar covers, center console, hood brackets, wind deflector, rear bulkhead trim and cover, I eventually found the connector fastened to a little bracket underneath the fuel tank near the fuel lines. What a mission. Got There though. Still cant find any new arms for this model though with the 10mm abs sensor hole. Fiat have stopped making them and all other manufacturers just list the other arm with bigger sensor.
I dodnt holed up much hope for being able to rebush the old arms either as I thing the bushes are different as well.........TBC

 

[ernibv]

So after stripping out the seats, sill trims, pillar covers, center console, hood brackets, wind deflector, rear bulkhead trim and cover, I eventually found the connector fastened to a little bracket underneath the fuel tank near the fuel lines. What a mission. Got There though. Still cant find any new arms for this model though with the 10mm abs sensor hole. Fiat have stopped making them and all other manufacturers just list the other arm with bigger sensor.
I dodnt holed up much hope for being able to rebush the old arms either as I thing the bushes are different as well.........TBC

OK. I think I warned you about this Buy new trailing-arms from Auto-Doc. ( I have no association with them, but they are magnificent ! The address says 'Berlin', but it's Berlin Poland )They are easy to replace and cost about euro 10 more than a revision-set. Solve all your problems in 1 project.
You are right that the new arms have a bigger hole. Nothing to do about that .... oh yeah ?
I did a left and right trailing-arm replacement ( from Auto-Doc ). I damaged the right ABS sensor at removal. Tried to be nice about it, but that didn't work. Destroyed the sensor. The left side was really simple: Hit the sensor squarely once with a small weighted hammer ( from the inside where it protrudes from the arm ). It will pop right out.
Replace the tailing-arm.
The next part takes more balls than brains
The existing sensor is a 90 degree installation with a lobe and small bolt. You can install it, but it is not deep enough to hang-out over the interior sensor part of the wheel-hub. You put it all back together and the ABS light stays on. That sucks.
So you have to trim the plastic so that it's 180 degrees. Use a little wire cutter. Nothing serious. It's old plastic that breaks away easily. ( more balls than brains ).
Buy some of this or an equivalent: https://www.bison.nl/nl/product/kombi-stick-portion-pack/6306555

Take 2 portions and prepare them separately. You don't have a lot of time, not much more than a few minutes.
Take 1 prepared portion and stuff it into the sensor hole on the tailing-arm. Use the other portion to make a collar for the sensor.
This part is important: take a flat piece of something ( I use the coffee stir things from the coffee-bar. 1.5 x 4 mm. Just smaller than the sensor ) and push it through the epoxy in the hole. Pull it out and push the sensor in. If all has gone well, the sensor-blade pushes through until it is actually not far enough to be completely over the wheel-bearing sensor. You now have about 60 seconds to put some pressure behind it and get the blade exactly where you want it: +/- 3mm above the interior wheel sensor. You should have a little bit of wiggle room to get it in place. Make sure to remove any epoxy on the inside. The distance between the sensor blade and the wheel-hub sensor is not really critical: enough space so that road debris does not accumulate.
I have done this 3 times; once as failure, twice as success
Good luck!
grtz
ER