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Discussion Starter · #1 · (Edited)
I have the ABS light permanently on on my 1.8 Rover 75 and have started checking the wheel sensors. The speedo is working OK so I am using the O/S sensor as a reference for the others. (Just to make sure, I disconnected the O/S sensor and sure enough the speedo stopped working).

My question is that I have tried to measure the resistance of each of the sensors using a dvm and they all read 'open circuit', even the known good O/S front! As I thought that they were just a simple inductive sensor (like on my wife's Ford when I had to replace a sensor) I expected something around 2K Ohms.

I am stumped, how do I test these things if they all read 'open circuit'????

Help!

PS Where is the ABS ECU located or is it part of the ABS hydraulic unit?
 

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Correct, it is part of the ABS module. These are prone to the connecter plug filling with water & corroding the pins - worth a check. i'll try & find a way of testing at work on Mon.
 

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You dont say wether the ABS is triggered when you press the brake pedal ?

Are any of the wiring harnesses from the sensors split/chaffed and "earthing" out on anything around them, if they are this will put the light on.
 

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Ooohhh I know where you're coming from - same type of bearing as fitted to a Peugeot 307! Get it in the right way round!!
Indeed - I only know because I had mine done a couple of weeks back and have had an ABS fault ever since. Changed cable - no joy. Found an ex master tech with T4 who checked things out and as you say said in every likelihood the new bearing has been put in the wrong way round :(

Need to go back to the original garage now and try to explain...
 

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Discussion Starter · #7 ·
No Bearing work

Sorry guys but no work has been done on the bearings and I have had the car for over four years.

Will check the ABS ECU connector and harness for damage or corrosion but I am still puzzled about the wheel sensors.
Does anyone know what form the signal is from these things?
In addition to the dvm I do have an old oscilloscope (!) which I did use on the wife's Ford to disgnose which sensor was faulty and how to fix it...
The Ford sensor detects the steps in the ring (reluctor do you call it?) The air gap between the sensor and the ring is CRITICAL. Using the 'scope I was able to find that one sensor was giving a weaker signal that the others. I removed it, filed away the rust that was holding the sensor slightly further away from the ring and bingo, full signal and fixed ABS (at no cost!!!!).
Ford sensors are relatively easy to remove and replace and reading threads on this site it seems that more often than not you have to destroy a Rover sensor to remove it - a costly process if you do not know which sensor is ar fault (it will be the last one you remove..... costly).

Which brings me back toi my question, how do you test the Rover sensors in situ??
 

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Hi All
I'm going trough the same proceedure at the moment.
ABS Light perminantley on.
Speedo ok. so offside front sensor is ok.
Near side front sensor open cct so assume duff. (no cruise on vehicle).
Tried to unplug offside sensor to measure its resistance but my hands are too big.
Got new front sensor off ebay it measures 1M7 ohms, fitted it but still got abs light.
Checked ABS Module connector, all clean and dry.
I assume I must have at least one duff rear sensor as well.

Correct me if I'm wrong, when you start the engine the ABS mudule looks for four wheel sensors by sensing their resistance, if all ok the light goes out. Then when you drive off, if one of the sensors does not record any pulses the ABS mudule will kill the ABS and turn the light back on. ??
Mick
 

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Before my R75 diesel,I had a rover 827 for 12 years and replaced 3 sensors over that time. It was easy to find the faulty sensor on that car by unplugging each one at a time and bridging the 2 contacts of the plug. Only one would put out the light. ie the faulty one. When the car was driven ,after a few yards the light came on again. I have not looked at the 75's plugs so perhaps that would not work. Maybe just too easy. The ohms on a new sensor on the 827 was 1600.
 
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