ABS woe

hinged_bap · 29th January 2018, 08:45

I've had ( intermittent ) low speed brake pedal crunch for some time now, the rear hubs have been renewed - amongst other things ( and the rusty backplates cleaned up to preclude rust flakes attaching to the reluctor rings ) but still no joy. After an inconclusive ABS pulse test session yesterday afternoon. Last night, the ABS fault light came on and I now have a solid ABS fault at static and out driving. This morning, I disconnected the rear o/s sensor ( at the connector at the rear of the back seat ) and connected a new one ( so obviously the new one isn't in contact with the reluctor ring ). My question is, if the rear o/s sensor was faulty, should the ABS pass static test with my fitting a new sensor in this fashion.
TIA
Bap

rustymotor · 29th January 2018, 09:37

Hi, I'm not expert far from it, it's not passing the static test. Where did the new sensor come from?

hinged_bap · 29th January 2018, 09:52

Quote:

Originally Posted by rustymotor

Hi, I'm not expert far from it, it's not passing the static test. Where did the new sensor come from?

I bought it from ebay, in fact, all sensors on the car ( of varying vintage ) came from ebay. Never paid more than £15.

rustymotor · 29th January 2018, 11:06

Hi, only ask because I had read that the ebay ones give a problem..you can check the voltage at the abs wire plugs blue cable should give 12 v momentarily using a cheap voltmeter, might help eliminate the abs unit.

chris75 · 29th January 2018, 11:38

Quote:

Originally Posted by hinged_bap

My question is, if the rear o/s sensor was faulty, should the ABS pass static test with my fitting a new sensor in this fashion.
TIA
Bap

Interesting question ! I would say yes it should as the circuit is present and correct whilst not moving , but I've never actually tried this . If you can get a TOAF or a T4 diagnostic test done , that will pinpoint your problem wheel . I have found TOAF very helpful in this respect

I am sure I have seen the particular substitution you have tried referred to on here before , but can't quickly find the thread ; a serious search on here might help

One last thought , the wheel may need to be spun or driven briefly to clear/reset the static test warning .

Roverpip · 29th January 2018, 12:14

Quote:

Originally Posted by hinged_bap

I've had ( intermittent ) low speed brake pedal crunch for some time now, the rear hubs have been renewed - amongst other things ( and the rusty backplates cleaned up to preclude rust flakes attaching to the reluctor rings ) but still no joy. After an inconclusive ABS pulse test session yesterday afternoon. Last night, the ABS fault light came on and I now have a solid ABS fault at static and out driving. This morning, I disconnected the rear o/s sensor ( at the connector at the rear of the back seat ) and connected a new one ( so obviously the new one isn't in contact with the reluctor ring ). My question is, if the rear o/s sensor was faulty, should the ABS pass static test with my fitting a new sensor in this fashion.
TIA
Bap

Hi Bap, some interesting info here:
http://http://www.macfadyen998.plus.com/

I had problems with my ABS not so long back. In answer to your question; ABS does a 4 sec test - ECU sends signal to each ABS sensor. If all ok, ABS light goes out, however if after driving a short distance, a fault occurs then ECU registers fault & illuminates ABS light.
If an ABS sensor goes faulty, then the ECU cuts power to the affected unit.

The test is in 3 parts.
1) strip back part of the cables into the ABS plug (see website link for colours)
solid colour is 12v constant, striped is pulse (could be other way round lol)
Using a volt meter, connect + to 12v constant - to good earth, this should give you a 12v reading.

2) raise relevant wheel off the ground. Connect voltmeter + to pulse cable - to ground. Spin the wheel and check readings - 0.67 rested & I think 1.74 with wheel turning. This determines sensor is reading the ring.

3) You'll need a donor set of ABS plug/socket. The idea is to 'bridge' the affected ABS to a known good cable i.e NSF ABS plugged into OSF socket. Its a way of kidding the ECU & usually works & can be good at determining faulty cabling.

My problem was a break somewhere in the loom. In the end I took new cable from the ECU to the affected ABS - hey presto, working ABS again.

Check under the battery compartment tray as this is where the ABS ECU lives & can get water damaged from plenum drain issues.

Another idea would be to disconnect the battery for 30 mins - as this can sometimes reset the ECU.

Hope this helps,
Phil.

cb750chris · 10th February 2018, 22:17

Hi David,
If you need any further hep with this, give me a shout and I will try and give you a hand - I can plug your car in on the T4 and we can home in on this fairly quickly (hopefully).
We can certainly sort this out, just a matter of time

Regards
Chris

kaiser · 11th February 2018, 09:12

I have had my ABS light on and no speedo for quite a while.
Yet the cruise function worked.
Yesterday I decided to give it some serious attention.

I took ear buds soaked in acetone, and cleaned the ring in the sensor hole. I know the front right wheel is responsible for the speedo.
The sensor senses from the side, so you try and clean the side of the bearing with the cotton bud while turning the wheel hub.

I must have used 6 buds both ends, and a lot of black greasy stuff cam off.
I tried a couple of times putting the wheel back, but no joy.
Then I dismantled the blue connector inside of the plastic wheel protector and sprayed some WD40 into the plug, and assembled it with a firm pressure.

Wupti, speedo works, ABS light gone.

So pay attention to the connector as well as the sensor. There is further a connector under the front seat that can give problems, but I didn't have to attend to that.

rustymotor · 11th February 2018, 09:59

I had the same problem with a Vauxhall 2 days before the MOT, cleaned the plugs with wd40 and bingo abs light gone..

lesternester · 11th February 2018, 16:50

I had also been having intermittent low speed brake pedal crunch and sometimes the abs light came on but last week my battery light came on and the alternator wasn't charging at all,i ran the car all week by charging the battery up every night,the thing is all week i've had no brake pedal crunch or abs light,yesterday i repaired the alternator with new regulator and brushes and the abs problems haven't reappeared.Maybe irregular power output from the failing alternator could be the cause of the abs problems.Just another thing that you could check,i had the same abs poblems on a previous 75 and never did cure the problem.Good luck.

29th January 2018, 08:45	#1
hinged_bap Gets stuck in 75 CDT Conn SE Auto saloon Join Date: Jun 2010 Location: Southampton Posts: 773 Thanks: 134 Thanked 104 Times in 81 Posts	ABS woe I've had ( intermittent ) low speed brake pedal crunch for some time now, the rear hubs have been renewed - amongst other things ( and the rusty backplates cleaned up to preclude rust flakes attaching to the reluctor rings ) but still no joy. After an inconclusive ABS pulse test session yesterday afternoon. Last night, the ABS fault light came on and I now have a solid ABS fault at static and out driving. This morning, I disconnected the rear o/s sensor ( at the connector at the rear of the back seat ) and connected a new one ( so obviously the new one isn't in contact with the reluctor ring ). My question is, if the rear o/s sensor was faulty, should the ABS pass static test with my fitting a new sensor in this fashion. TIA Bap

10th February 2018, 22:17	#7
cb750chris Trader Rover 75 Tourer Join Date: Apr 2011 Location: Portsmouth Posts: 849 Thanks: 201 Thanked 292 Times in 200 Posts	Hi David, If you need any further hep with this, give me a shout and I will try and give you a hand - I can plug your car in on the T4 and we can home in on this fairly quickly (hopefully). We can certainly sort this out, just a matter of time Regards Chris __________________ Now offering T4 services in the Fareham area Replacement keys programmed / supplied / cut Diesel 135 upgrade available IPK virginisation and T4 matching available Sorry, due to a big change in home circumstances, I am unable to do any large jobs at present, but can still offer evening time diagnostics.

11th February 2018, 09:12	#8
kaiser This is my second home 75 Tourer 2.5 Auto, 1.8T, 75V8ZT Join Date: Jun 2007 Location: Johannesburg ZA Posts: 6,200 Thanks: 1 Thanked 859 Times in 613 Posts	I have had my ABS light on and no speedo for quite a while. Yet the cruise function worked. Yesterday I decided to give it some serious attention. I took ear buds soaked in acetone, and cleaned the ring in the sensor hole. I know the front right wheel is responsible for the speedo. The sensor senses from the side, so you try and clean the side of the bearing with the cotton bud while turning the wheel hub. I must have used 6 buds both ends, and a lot of black greasy stuff cam off. I tried a couple of times putting the wheel back, but no joy. Then I dismantled the blue connector inside of the plastic wheel protector and sprayed some WD40 into the plug, and assembled it with a firm pressure. Wupti, speedo works, ABS light gone. So pay attention to the connector as well as the sensor. There is further a connector under the front seat that can give problems, but I didn't have to attend to that. __________________ Worth his V8 in gold

29th January 2018, 09:37	#2
rustymotor Posted a thing or two Rover 75 Tourer Join Date: May 2017 Location: Hull Posts: 1,848 Thanks: 216 Thanked 432 Times in 340 Posts	Hi, I'm not expert far from it, it's not passing the static test. Where did the new sensor come from?

29th January 2018, 11:06	#4
rustymotor Posted a thing or two Rover 75 Tourer Join Date: May 2017 Location: Hull Posts: 1,848 Thanks: 216 Thanked 432 Times in 340 Posts	Hi, only ask because I had read that the ebay ones give a problem..you can check the voltage at the abs wire plugs blue cable should give 12 v momentarily using a cheap voltmeter, might help eliminate the abs unit.

11th February 2018, 09:59	#9
rustymotor Posted a thing or two Rover 75 Tourer Join Date: May 2017 Location: Hull Posts: 1,848 Thanks: 216 Thanked 432 Times in 340 Posts	I had the same problem with a Vauxhall 2 days before the MOT, cleaned the plugs with wd40 and bingo abs light gone..

11th February 2018, 16:50	#10
lesternester Newbie MG ZT Join Date: Feb 2015 Location: Norfolk Posts: 15 Thanks: 1 Thanked 0 Times in 0 Posts	I had also been having intermittent low speed brake pedal crunch and sometimes the abs light came on but last week my battery light came on and the alternator wasn't charging at all,i ran the car all week by charging the battery up every night,the thing is all week i've had no brake pedal crunch or abs light,yesterday i repaired the alternator with new regulator and brushes and the abs problems haven't reappeared.Maybe irregular power output from the failing alternator could be the cause of the abs problems.Just another thing that you could check,i had the same abs poblems on a previous 75 and never did cure the problem.Good luck.