Help diagnosing an ABS fault on my Dad's old Rover 75 - Page 2

WayneH · 6th March 2017, 18:44

Quote:

Originally Posted by neilll

As already stated if your cruise is not working it will be your front nearside sensor that is u/s!

Neil

Thanks Neil, but I am not confident enough with the diagnosis at this stage. As I said above, the cruise has not worked for a long time as far as I know whereas the ABS issue only started recently. I am therefore not convinced the two faults are linked at this stage.

Sector-9 · 7th March 2017, 05:40

The ABS ECU will log all faults until it's memory is cleared, though the light may go out if the fault isn't present at next startup test. And TOAF works well on the 75 despite all but the newest cars not being EOBD compliant, though you can usually get very limited live engine data from them with a generic EOBD reader anyway.

Synchromesh · 7th March 2017, 12:13

I recently had the same problem as you. The rear off side brake was seized making the wheel/hub very hot at exactly the same time that the ALB problems started so I assumed the heat had damaged the magnets in the bearing. I freed the rear off side brake and fitted a new rear off side hub. This did not resolve the ALB problem. I then made a cable that allowed me to start the engine with the rear ALB sensor output signals connected to their normal brake computer inputs to pass the stationary ALB test but then switch the rear off side ALB sensor output such that it supplier both brake computer rear brake inputs. This passed the moving ALB test and stopped the pedal judder and clicking but the ALB still worked if I braked on a slippery surface. This gave me the confidence to fit a new hub on the rear near side and all the ALB problems are now fixed.

WayneH · 13th March 2017, 19:30

Quote:

Originally Posted by Sector-9

The ABS ECU will log all faults until it's memory is cleared, though the light may go out if the fault isn't present at next startup test. And TOAF works well on the 75 despite all but the newest cars not being EOBD compliant, though you can usually get very limited live engine data from them with a generic EOBD reader anyway.

OK, thanks Darren - that's useful information. What is the quick solder modification that I need to do if I get one of those cables that you suggested? As I said, I have a similar cable for my Mitsubishi, which also had a quick solder modification - hopefully it will be the same mod!

Quote:

Originally Posted by Synchromesh

I recently had the same problem as you. The rear off side brake was seized making the wheel/hub very hot at exactly the same time that the ALB problems started so I assumed the heat had damaged the magnets in the bearing. I freed the rear off side brake and fitted a new rear off side hub. This did not resolve the ALB problem. I then made a cable that allowed me to start the engine with the rear ALB sensor output signals connected to their normal brake computer inputs to pass the stationary ALB test but then switch the rear off side ALB sensor output such that it supplier both brake computer rear brake inputs. This passed the moving ALB test and stopped the pedal judder and clicking but the ALB still worked if I braked on a slippery surface. This gave me the confidence to fit a new hub on the rear near side and all the ALB problems are now fixed.

Thanks Stephen, that's useful information. I may end up trying this as well. Presumably I would need three blue ABS connectors (2 female and 1 male) to make up such a cable?

Sector-9 · 13th March 2017, 19:36

I don't remember off the top of my head, but I think you need to bridge pins 7 & 8 on the OBD plug (on the lead, not the car), otherwise TOAF won't be able to see all the car's ECUs. I strongly suggest searching this site for the exact pins though as you can destroy electronics if you bridge the wrong ones.

WayneH · 13th March 2017, 19:39

Quote:

Originally Posted by Sector-9

I don't remember off the top of my head, but I think you need to bridge pins 7 & 8 on the OBD plug (on the lead, not the car), otherwise TOAF won't be able to see all the car's ECUs. I strongly suggest searching this site for the exact pins though as you can destroy electronics if you bridge the wrong ones.

Thanks, I will investigate - it sounds like a different mod to the one I did for the Mitsubishi cable. Shame, I could have had a common cable for both cars.

WayneH · 18th March 2017, 19:06

Made some progress diagnosing the ABS fault today.

Thanks to Mickyboy, who posted me some ABS connectors, I was able to make up a test loom to do a static test of the wheel sensors. I only checked the rears and believe the OSR is at fault.

The picture below shows the results of my testing on the NSR. The chalk marks show points on the rotation where the wheel sensor voltage changed from 1.7v to 0.7v. As you can see, all was OK this side. Doing the same test on the OSR, I had no changes in voltage - it remained at 1.7v the whole time. I repeated the test 3 times to make sure I had not made a mistake.

So, it does indeed appear that the fault is caused by a implausible signal coming from the OSR wheel sensor. So, what should I do next, remove the hub and take a look - or just go ahead and order a replacement rear hub for the OSR?

FrenchMike · 18th March 2017, 19:36

Well done, not sure the sensor is faulty (replacing not easy) ,so i would firstly have a closely look at the hub /bearing .

Mike

Avulon · 18th March 2017, 23:44

dismantle and clean, the retest it's not too big a job to do that - you won't have to completely reassemble just to see if cleaning makes a difference - it might just be rust flakes got into the gap betwen sensor and bearing.

WayneH · 25th March 2017, 17:49

Spent some more time trying to diagnose the ABS fault today. Having confirmed that the OSR is at fault, I removed the hub so that I could look at the end of the sensor and the hub itself. The photos below show the sensor, the backplate and the rear of the hub:

I gave the end of the sensor and the pick up area on the back of the hub a good clean:

I then refitted the hub and the hub nut, securing it to the correct torque and retested. Unfortunately, the problem was not fixed. The clean up did make a small difference, as I was getting one or two voltage changes from 1.60v to 0.64v per revolution of the hub but nothing like what I was getting when I tested the NSR.

So, what do you recommend I do next? Should I replace the hub or is it possible that the backplate is the issue, as it does have some corrosion? If I replace the hub, I was thinking about trying a second hand one, in case it turns out not to fix it - however, if I decide to get a new one, what makes should I avoid - or can anyone recommend how much I should spent to get a decent replacement?

Thank you

7th March 2017, 05:40	#12
Sector-9 Gets stuck in Rover 75 CDT manual Tourer Join Date: Aug 2014 Location: nr. Mansfield Posts: 767 Thanks: 24 Thanked 182 Times in 137 Posts	The ABS ECU will log all faults until it's memory is cleared, though the light may go out if the fault isn't present at next startup test. And TOAF works well on the 75 despite all but the newest cars not being EOBD compliant, though you can usually get very limited live engine data from them with a generic EOBD reader anyway. __________________ Free fault codes scan/clear (TOAF) - M1 J27 area

13th March 2017, 19:36	#15
Sector-9 Gets stuck in Rover 75 CDT manual Tourer Join Date: Aug 2014 Location: nr. Mansfield Posts: 767 Thanks: 24 Thanked 182 Times in 137 Posts	I don't remember off the top of my head, but I think you need to bridge pins 7 & 8 on the OBD plug (on the lead, not the car), otherwise TOAF won't be able to see all the car's ECUs. I strongly suggest searching this site for the exact pins though as you can destroy electronics if you bridge the wrong ones. __________________ Free fault codes scan/clear (TOAF) - M1 J27 area

18th March 2017, 19:36	#18
FrenchMike This is my second home Rover 75 Saloon Join Date: Aug 2007 Location: Avignon Posts: 4,466 Thanks: 94 Thanked 661 Times in 554 Posts	Well done, not sure the sensor is faulty (replacing not easy) ,so i would firstly have a closely look at the hub /bearing . Mike Last edited by FrenchMike; 18th March 2017 at 20:03..

18th March 2017, 23:44	#19
Avulon This is my second home 1.8t Tourer Join Date: Oct 2011 Location: Tanelorn Posts: 4,830 Thanks: 956 Thanked 1,148 Times in 916 Posts	dismantle and clean, the retest it's not too big a job to do that - you won't have to completely reassemble just to see if cleaning makes a difference - it might just be rust flakes got into the gap betwen sensor and bearing. __________________ Need a T4 ?: T4 Owners Map thanks to Stevestrat ( use at your own risk) Where?: https://en.wikipedia.org/wiki/Tanelorn Mods/Retrofits: PCV vortex 'filter'; bluetooth; inline thermostat; reversing sensors; plenum spyhole ; headlamp washers ; Diy mp3 player replacing CD multichanger; FBH with remote; Headlamp washers; black/chrome front grille, rear blind; Xenon projectors To do: puddle lights; 2 Din cd/nav to fit; boot release button

7th March 2017, 12:13	#13
Synchromesh Gets stuck in Rover 75 Saloon Join Date: Jan 2010 Location: Preston Posts: 624 Thanks: 50 Thanked 44 Times in 32 Posts	I recently had the same problem as you. The rear off side brake was seized making the wheel/hub very hot at exactly the same time that the ALB problems started so I assumed the heat had damaged the magnets in the bearing. I freed the rear off side brake and fitted a new rear off side hub. This did not resolve the ALB problem. I then made a cable that allowed me to start the engine with the rear ALB sensor output signals connected to their normal brake computer inputs to pass the stationary ALB test but then switch the rear off side ALB sensor output such that it supplier both brake computer rear brake inputs. This passed the moving ALB test and stopped the pedal judder and clicking but the ALB still worked if I braked on a slippery surface. This gave me the confidence to fit a new hub on the rear near side and all the ALB problems are now fixed.

18th March 2017, 19:06	#17
WayneH Newbie Skoda Fabia Join Date: Dec 2016 Location: Bracknell Posts: 26 Thanks: 20 Thanked 7 Times in 6 Posts	Made some progress diagnosing the ABS fault today. Thanks to Mickyboy, who posted me some ABS connectors, I was able to make up a test loom to do a static test of the wheel sensors. I only checked the rears and believe the OSR is at fault. The picture below shows the results of my testing on the NSR. The chalk marks show points on the rotation where the wheel sensor voltage changed from 1.7v to 0.7v. As you can see, all was OK this side. Doing the same test on the OSR, I had no changes in voltage - it remained at 1.7v the whole time. I repeated the test 3 times to make sure I had not made a mistake. So, it does indeed appear that the fault is caused by a implausible signal coming from the OSR wheel sensor. So, what should I do next, remove the hub and take a look - or just go ahead and order a replacement rear hub for the OSR?

25th March 2017, 17:49	#20
WayneH Newbie Skoda Fabia Join Date: Dec 2016 Location: Bracknell Posts: 26 Thanks: 20 Thanked 7 Times in 6 Posts	Spent some more time trying to diagnose the ABS fault today. Having confirmed that the OSR is at fault, I removed the hub so that I could look at the end of the sensor and the hub itself. The photos below show the sensor, the backplate and the rear of the hub: I gave the end of the sensor and the pick up area on the back of the hub a good clean: I then refitted the hub and the hub nut, securing it to the correct torque and retested. Unfortunately, the problem was not fixed. The clean up did make a small difference, as I was getting one or two voltage changes from 1.60v to 0.64v per revolution of the hub but nothing like what I was getting when I tested the NSR. So, what do you recommend I do next? Should I replace the hub or is it possible that the backplate is the issue, as it does have some corrosion? If I replace the hub, I was thinking about trying a second hand one, in case it turns out not to fix it - however, if I decide to get a new one, what makes should I avoid - or can anyone recommend how much I should spent to get a decent replacement? Thank you