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Old 6th May 2021, 16:44   #1
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Default ABS problem is hurting my brain

Hi folks,

Well, what I thought was a routine ABS sensor failure is not. When I bought the car the ABS warning light would come on sometimes when the car was started. and always go away after the second start of the day. Then it would stay gone.

As time went on the light would stay on every morning until the restart after driving for a few minutes. Then it progressed to having to drive further before the restart. Finally, it got to the point it is at now - the light just stays on.

When the light is on the cruise control doesn't work. That points to the left front sensor failure or wiring problem. Braking stays normal and feels smooth. You'd never say anything was wrong apart from the warning light. Of course, I'm sure the ABS wouldn't function.

The last time I was the in Slovakia I had the left front sensor changed and the hub cleaned up. It wasn't bad at all. BUT, the new sensor caused immediate roughness and noise when braking normally. We put the original sensor back in and normal, quiet, smooth braking resumed - undoubtedly without functioning ABS. This was the fall of 2019.

My friend just had the new BEBI-Bilstein Made in Germany sensor installed today. The warning light still stays on. That's an MOT fail. He will ask them to drive the car out in their parking lot tomorrow to see if braking feels normal with this new sensor or not. They also cleaned all 4 hubs.

So, now I am at a loss. Can someone advise the next step, please?

Thank you,
Glenn
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Old 6th May 2021, 17:18   #2
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I'd just run Toaf and see if it agrees with your left front suspicions. Then either change sensor or bearing, or both. Some sensors are better than others, some require bits shaved off them to move the sensors closer to the bearing's magnetic strip. I know DMGRS have original rear sensors (ordered a couple as can't get better than original), someone might be able to advise on good front sensors.

Good luck

PS. Link to Best of British, says they are MG/Rover sensors: https://www.ebay.co.uk/itm/265017968...QAAOSwcCdgBXOW

Last edited by vitesse; 6th May 2021 at 19:09..
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Old 7th May 2021, 02:40   #3
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Quote:
Originally Posted by vitesse View Post
I'd just run Toaf and see if it agrees with your left front suspicions. Then either change sensor or bearing, or both. Some sensors are better than others, some require bits shaved off them to move the sensors closer to the bearing's magnetic strip. I know DMGRS have original rear sensors (ordered a couple as can't get better than original), someone might be able to advise on good front sensors.

Good luck

PS. Link to Best of British, says they are MG/Rover sensors: https://www.ebay.co.uk/itm/265017968...QAAOSwcCdgBXOW
Thank you, Mike. We will see what happens in the morning.

Glenn
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Old 7th May 2021, 14:03   #4
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Well, small update. They put a scan tool on it and saw a fault of a broken wire or no contact. Now, this is a translation, but I know what they mean. I have to give him a call to see if the tool identified a location.

BUT, he changed the 10A fuse and the warning light went off. There will have to be more investigation. The fuse is obviously not the cause of the ongoing and worsening problem. I suppose it is possible there was an unintended momentary short while taking it apart or putting it together yesterday that blew the fuse.

Cheers,
Glenn
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Old 7th May 2021, 14:33   #5
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You say that the anti-lock system doesn't work.--Have you tried braking hard at a low speed on a loose gravel surface to test it ???---Or, because of the light, you just assume the system isn't working.----
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Old 7th May 2021, 14:48   #6
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I believe the voltages used by the sensors are very low, and I have trouble seeing that the fuse has blown because of taking things apart and putting them back together, though I could be wrong. Have you checked the condition of the ABS plug?

Keep well
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Old 7th May 2021, 14:52   #7
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This is what I found when I had ABS problems
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Old 7th May 2021, 16:20   #8
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Quote:
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You say that the anti-lock system doesn't work.--Have you tried braking hard at a low speed on a loose gravel surface to test it ???---Or, because of the light, you just assume the system isn't working.----
It had been playing up over time and getting worse to the point of full time fault. Normal braking was normal, haven't tried ABS, but with the warning light on and cruise control U/S, I figured the ABS wouldn't function either. The big deal is the MOT being due and the ABS warning light being on is an automatic fail.

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I believe the voltages used by the sensors are very low, and I have trouble seeing that the fuse has blown because of taking things apart and putting them back together, though I could be wrong. Have you checked the condition of the ABS plug?

Keep well
Well, I'm not actually there and doing the work. My friend is. I'm still stuck in Canada. I thought maybe a damaged plug, careless handling of the powered end of an open plug or even a situation like in Suzublu's picture below may blow the fuse. Just wishful thinking, really. I don't really believe the fuse was the main fault, but must have been collateral damage during the work.

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Originally Posted by suzublu View Post
This is what I found when I had ABS problems
Yeah, I looked for that when I had it apart in the Fall of 2019, but only at the front. I was sure it was the left front sensor. I didn't look at the rear cables then.

Cheers,
Glenn
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Old 7th May 2021, 20:32   #9
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Quote:
Originally Posted by slovcan View Post
It had been playing up over time and getting worse to the point of full time fault. Normal braking was normal, haven't tried ABS, but with the warning light on and cruise control U/S, I figured the ABS wouldn't function either. The big deal is the MOT being due and the ABS warning light being on is an automatic fail.

Yeah, I looked for that when I had it apart in the Fall of 2019, but only at the front. I was sure it was the left front sensor. I didn't look at the rear cables then.

Cheers,
Glenn

Absolutely correct, once the light is on the ABS is disabled end of, it is brought on by the system when a fault is registered from one of, or several of, many components from sensors, pump, modulator, wiring and so on.
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Old 10th May 2021, 12:44   #10
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Hi folks,

I have another update and some collective thinking from my friend who is looking after the car and I.

He says he couldn't see that the fuse he replaced had blown, but did not meter it.

The warning light is turning off again after a warm restart just as was happening when I first got the car (until that resolution deteriorated over time). I think it is likely the fuse was NOT blown, shutting the car off and replacing the fuse resulted in a warm restart which resulted in the warning light turning off.

I had assumed (I know, I should not do that) that because the cruise control failed when the warning light was on the fault must have been the left front sensor. When I replaced that the result was the grinding noisy braking of a surely bad new sensor right out of the box. Putting the original back in resulted in smooth normal braking albeit with the warning light on. The hub was well cleaned when the new sensor was installed. That original sensor has now been replaced again with the brand new made in Germany FEBI-Bilstein one. At that time all four hubs and reluctor rings were cleaned. I'm thinking now maybe the original sensor was fine and not the cause of the warning light. Still, with the light on the cruise control does not function, but braking feels normal, smooth and quiet.

The scan tool identified a broken wire or contact. We know it seems to resolve itself when the car is warmed up and engine restarted. When cold the fault shows as the warning light staying on when the engine is started. To me that sounds like a failed self-test.

So, all ye of more experienced brains than I, can you think of anything that would cause a loss of contact when cold but have contact restored when the engine is warm AND give the symptom of inoperative cruise control? I am not there so have to rely on my friend to do the work. He is very capable - to the point that he is rebuilding/restoring a Fiat X1/9 for himself. I normally would not just throw parts at a problem, but I am not there and we have less than 2 weeks to get the inspection passed. So, if parts may help, I'll get them.

Guys, I really need help with this. I have sent him the Service Manual and given him the relevant page numbers to get him started, but time is the enemy. I did suggest he get to the ABS Modulator/ECU and unplug/re-plug the connector a few times and maybe spray some contact cleaner in it.

Thank you,
Glenn
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