ABS fault with a twist !

[terranosauruschris]

Hi, guys... please put thinking caps on 'cos I can't figure this one at all :
Got NO indication of any ABS fault on dash, but every now and again when I brake, get terrible scraping/vibrating feeling back through, the pedal...this disappears after 2 or 3 secs of pedal pressure and normal braking is resumed for an hour or two.
Apart from the obvious danger, it's doing my head in!! Any clues, please?
:nenau

 

[Kamsin]

Possible of rust or grit in the brakes, have you taken them off and checked/cleanded them out. :doh

 

[terranosauruschris]

Yes, done that, cleaned it all up, replaced pads with new, even had a DTI on discs to check for run-out... took fuse out for a couple days when it was nice and dry, the fault never surfaced...replaced fuse and it's straight back!

 

[rayf3262]

If the ABS believes a wheel has stopped turning when braking due to a missing or intermittent sensor signal then the ABS will be brought into play:

there was a member on here who found one of the front driveshafts had "floated" inwards thus moving the ABS cogged wheel away from the sensor, this, I believe, was due to a missing circlip on the hub somewhere.

 

[terranosauruschris]

That's a really interesting theory and may explain why I've got no dash indication.
Will investigate soonest, thanks Ray.:clap

 

[extreme-4x4]

If the ABS believes a wheel has stopped turning when braking due to a missing or intermittent sensor signal then the ABS will be brought into play:

there was a member on here who found one of the front driveshafts had "floated" inwards thus moving the ABS cogged wheel away from the sensor, this, I believe, was due to a missing circlip on the hub somewhere.

but he should have fixed hubs , is there a cir clip in those models?

 

[rayf3262]

but he should have fixed hubs , is there a cir clip in those models?

yes, there is.
It's the first thing you see after removing the cap from the drive flange.
Also, they are available in about 6 differing thicknesses (0.2mm increments) to adust the drive shaft position.

 

[extreme-4x4]

very handy info

 

[glanrichbex]

Just to revisit this one - My ABS was disconnected when I bought my Terrano, someone had put a piece of black tape over the ( ! ) handbrake / servo vacuum / fluid level lamp and no ABS light on ignition.
On investigation I found the ABS fuse had been removed fdrom the interior fuse box and replacing it brought on vibration from the brake pedal when comming to a stop.

When I removed the instrument unit , I found the LED behind the ABS light had been broken off - sure enough when I replaced it the light is on all the time!!:banghead

I have traced the fault to an open circuit sensor on the off side front, on testing with a multimeter it is open circuit??? does anyone know what resistance it should be?

 

[geoffdown]

Just to revisit this one - My ABS was disconnected when I bought my Terrano, someone had put a piece of black tape over the ( ! ) handbrake / servo vacuum / fluid level lamp and no ABS light on ignition.
On investigation I found the ABS fuse had been removed fdrom the interior fuse box and replacing it brought on vibration from the brake pedal when comming to a stop.

When I removed the instrument unit , I found the LED behind the ABS light had been broken off - sure enough when I replaced it the light is on all the time!!:banghead

I have traced the fault to an open circuit sensor on the off side front, on testing with a multimeter it is open circuit??? does anyone know what resistance it should be?

No but not open circuit there was a guy on here who fixed the sensor as with his there was broken wires in the cable from the sensor (sounds like ur problem open circuit) he fixed them together and it worked fine new sensor I think was around £350 ish good luck with ur problem.

 

[glen]

REPAIRING SENSORS (1.1ohms to 1.3 ohms off the top of my head)

The sensor is a problem on T2 See below

REPAIRING SENSORS

your old sensor can easily be repaired the sensor very rarely goes wrong its the wiring that connects it that breaks down and can be replaced by a competent DIY person or an auto electrician with very little kit needed you need a multimeter a soldering iron and solder some heat shrink (resin sealing is best) and some cable.

1. Too find the faulty sensor jack up and support the front of the vehicle on axel stands and remove the front wheels.

2. disconnect both front sensors from behind the rubber splash guard (follow the cable to the chassis) and unbolt the brackets that hold it to the suspension (do not remove the sensors from the hub as they will be rusted solid and you will damage them getting them out )

3. switch on your multi meter and set it to ohms connect the two leads to the two connectors inside the plug of the sensor lead (it doesn't mater which way round ) you should get a reading (1.1ohms to 1.3 ohms off the top of my head) get some body to hold the plug and multimeter leads while you wiggle the cable if the reading on the multimeter changes that is the faulty sensor you may have to bend the cable quite tight to find the broken wire its usually in the last bit of protective sleving (rubber hose ) before the sensor.

when you find the faulty one lay it on a piece of cardboard and mark the positions of the sleving and the brackets as you will need to remove these and put them back on later you can prixe the metal brackets off with a screw driver and after cutting the plug off the end of the sensor lead (leave a bit of cable to reconnect it) you can slide the sleving off with a bit of wd40

cut open the protective casing of the twin core cable and strip it back revealing the two cables work your way to the sensor you will probably see the broken wire just after the break cut the cable and find a length of new cable of the same size (this is important) there are plenty of car electrical shops that will help you solder the new cable onto the sensor and cover the join with heatshrink i use one that seals its self with a resin when you shrink it to make it water proof then cover both cables in heatshrink to form another protective layer and replace the rubber sleving anf support brackets and solder the plug back on the end and use heatshrink to seal it again reattach the support brackets and reconnect the plug replace the wheels and the job should be done make sure you check both sides as they may have both gone.

when you test it switch on the ignition and start the engine the light will come on for a few seconds then go out the pump under the bonnet will hiss once then stop road test the vehicle the light should stay off and the pump should not hiss under the bonnet.

hope this helps if not you will have to search the breakers for a second hand one which may not be in any better condition and they are as rare as rocking horse pooh trust me i have looked for one!

another thing that can effect it is the slotted ring that turns with the front hub the sensor has a magnet inside it and when this slotted ring turns it senses it and tells the abs Ecu the speed at which the wheel is turning the Ecu monitors all the wheel speeds if the abs senses that a wheel is about to skid it turns the brakes off it activates the abs mode on that wheel. The trouble is the slotted ring gets clogged with mud grease and metal fillings from the brakes and the sensor is fooled into thinking the wheel is skidding.

POWER SUPPLIE FUSES
Check fuses, 21-10amp, 25-10amp, 28-10amp, 49-20amp and fuse 50-10amp these are power supplies to NATS and the ECM.

Glen

 

[Maxwell]

Excellent post....

 

[spudd]

If the ABS believes a wheel has stopped turning when braking due to a missing or intermittent sensor signal then the ABS will be brought into play:

there was a member on here who found one of the front driveshafts had "floated" inwards thus moving the ABS cogged wheel away from the sensor, this, I believe, was due to a missing circlip on the hub somewhere.

That was me. but i did have abs light on it turned out previous owner had filled light with black silicone.

 

[glanrichbex]

Many thanks Glen for an excellent post.:thumb2

I am an electronics engineer by trade and I never thought of repairing the wires :doh

I will give it a go this week end!

 

[terranosauruschris]

Some great ideas for me to work on, guys, many thanks, have been on hols for a fortnight (not in car ! ), gotta get the beast sorted cos MOT's coming soon, will post results. Mucho grassyarse!:bow

 

[supergnome]

Well, if Glen's post aint worth your tenner subs then what is. Replaced on mine by previous owner cost him £129. David.