Technical ABS Light On

[Shuheb]

Hi, I'm new here and experiencing some difficulty with my Fiat Grande Punto 1.2 2007, the abs light is on and when scanning it shows the Front Right sensor not reading, I confirmed this by individually testing each wheel sensor and all wheels apart from the front right show a speed reading on the scanner, so I replaced the sensor thinking the problem would be fixed however it did not, when I tried clearing the fault codes the ABS light would come straight back on when the car would start moving. So I digged around the forum to find related issues and found that checking the main plug and wiring could be at fault. So I checked all the connections from the Sensor Plug back to the Big Plug near the pump. I checked all the connections and they were all mint and did a continuity test from the Front Right Sensor Plug back to the Big Plug and all the readings were fine. Does anyone have any idea what the issue could be as i am starting to lose hope... Any help would be much appreciated!!

 

[bugsymike]

Hi, I'm new here and experiencing some difficulty with my Fiat Grande Punto 1.2 2007, the abs light is on and when scanning it shows the Front Right sensor not reading, I confirmed this by individually testing each wheel sensor and all wheels apart from the front right show a speed reading on the scanner, so I replaced the sensor thinking the problem would be fixed however it did not, when I tried clearing the fault codes the ABS light would come straight back on when the car would start moving. So I digged around the forum to find related issues and found that checking the main plug and wiring could be at fault. So I checked all the connections from the Sensor Plug back to the Big Plug near the pump. I checked all the connections and they were all mint and did a continuity test from the Front Right Sensor Plug back to the Big Plug and all the readings were fine. Does anyone have any idea what the issue could be as i am starting to lose hope... Any help would be much appreciated!!

Assuming the ABS sensor was the correct one for your model, there is passive and active sensors, active ones will show a voltage across the two pins of the plug going to the sensor, usually just below battery voltage. Sometimes but not always an active one if faulty the fault when cleared will return even without driving the car.
The older cars had a visible vane ring which could rust or get damaged , they were for Hall type ABS sensors
I spent ages on a Skoda Scout and was told by the motor factors there was only one sensor for that 4x4 model and finally got the right one using a VW Tiguan 4x4 one which said about a choice of two. I had already gone down the route of wiring lead replacement, even a wheel bearing as they have a magnetic ABS ring in the back of the bearing, which incidentally if you have had a bearing changed or even if someone fitted a cv boot kit and prodded the back of the wheel bearing with a magnetised screwdriver can damage the ABS ring. On the Skoda I finally located the fault in the main wiring loom where it went to the ABS pump Control Unit.
If you suspect the wheel bearing magnetic ABS ring I used a test card from SKF bearing company which can show if there is a fault there. There is a thread I replied to a few days ago where I showed a photo of it working to test.
There is quite a few relevant but not Fiat based details on the web about ABS issues.

 

[Shuheb]

Assuming the ABS sensor was the correct one for your model, there is passive and active sensors, active ones will show a voltage across the two pins of the plug going to the sensor, usually just below battery voltage. Sometimes but not always an active one if faulty the fault when cleared will return even without driving the car.
The older cars had a visible vane ring which could rust or get damaged , they were for Hall type ABS sensors
I spent ages on a Skoda Scout and was told by the motor factors there was only one sensor for that 4x4 model and finally got the right one using a VW Tiguan 4x4 one which said about a choice of two. I had already gone down the route of wiring lead replacement, even a wheel bearing as they have a magnetic ABS ring in the back of the bearing, which incidentally if you have had a bearing changed or even if someone fitted a cv boot kit and prodded the back of the wheel bearing with a magnetised screwdriver can damage the ABS ring. On the Skoda I finally located the fault in the main wiring loom where it went to the ABS pump Control Unit.
If you suspect the wheel bearing magnetic ABS ring I used a test card from SKF bearing company which can show if there is a fault there. There is a thread I replied to a few days ago where I showed a photo of it working to test.
There is quite a few relevant but not Fiat based details on the web about ABS issues.

Hi, Thanks for the reply,
I assumed they are active sensors as they have to be plugged in, where the wiring leads to the ECU, I checked the other sensors that work, with the new sensor I bought, and they were identical. I originally assumed the part was faulty but I'm now 3 new ABS sensors deep so it deffo can't be the sensor and I'm sure it is not the connection between the plug and ECU as I have checked all the wires and tested the connections with meter readings. I think with your suggestion the only option I have left would be the bearing, will take it to a garage and get it replaced and pray that the problem get's solved.

Thanks again.

 

[bugsymike]

Did you put a voltmeter to check at ABS sensor plugs?
Try and be certain before condeming the bearing, I replaced the one on the Skoda and was wrong.
This is the test card I mentioned in another thread. https://www.fiatforum.com/attachments/dscf0746-jpg.421115/

 

[Shuheb]

Did you put a voltmeter to check at ABS sensor plugs?
Try and be certain before condeming the bearing, I replaced the one on the Skoda and was wrong.
This is the test card I mentioned in another thread. https://www.fiatforum.com/attachments/dscf0746-jpg.421115/

Yeah I put two copper wires in the pins of the plug under the wheel arch and put copper wires in each individual pin hole on the big plug (ecu) until I found which holes they connect to and managed to get readings. Used copper wires as the red/black metal points did not fit in the holes. Will try out the test card, must be the bearing as I can not see any other faults anywhere. Lucky bearing is pretty cheap for fiat, only labour costs I got to worry about.

 

[bugsymike]

Yeah I put two copper wires in the pins of the plug under the wheel arch and put copper wires in each individual pin hole on the big plug (ecu) until I found which holes they connect to and managed to get readings. Used copper wires as the red/black metal points did not fit in the holes. Will try out the test card, must be the bearing as I can not see any other faults anywhere. Lucky bearing is pretty cheap for fiat, only labour costs I got to worry about.

If the ABS wiring plug is undone on my Skoda I got a 11Vt reading from the good side but only around 8vt from the faulty one.
Aparently on that model water runs up the plug in the wheel arch and corrodes the wires, mine was more expensive as it did ABS, brake pad wear indicator and also a YAW sensor for the ESP control. The annoying bit was the genuine repair section from the dealers only goes to the start of the main loom and the fault was much further in, so in the end I had to make up an extra length to take it all the way to the ABS module unit.
Don't forget to keep anything magnetic away from the bearing if it has the ABS rotor in the bearing like my photo.