Help diagnose abs problem please. G Sensor?

[theron]

I know this is an old thread but I've recently had this problem so thought I'd add my experience to it so that anyone searching this problem finds it:

I had the ABS warning light come on intermittantly - for seemingly no reason. The warning would always come on with the ignition and then go out after starting but then would come on at some point. It got to the stage where it was happening on every journey. While the light was out the ABS worked fine.

I took the car to a local Bosch garage who read a code 22 and looking this up in the workshop manual it's a open circuit to the front offside sensor.

I traced the wiring and followed the advice here and identified the pink and blue wires in the loom. The loom runs along the top of the bulkhead all the way across the back of the engine bay. The pink/blue wires run from a connector near the ABS controller and then branch off halfway along the bulkhead, past the intercooler (not under it in my case) and then join a plug at the top front of the engine.

The wires looked undamaged but by flexing the loom where it branches off the bulkhead while monitor the resitance across pins 4&5 (of the ABS connector to the contoller) the resistance jumped from about 1.7K ohms to open circuit. I open up the loom, replaced as much of the pink/blue wires (they are a twisted pair) as I could get to and packed the loom back up. The ABS light hasn't come on the last few journeys I've done so hopefully this has fixed the problem.

The garage wanted to charge £370 for a new sensor.

 

[mully]

Did replacing the pink/blue wires in your wiring loom cure the intermittent abs light problem, as i have same problem, allready spent £300 on it

 

[theron]

Yes it did. ABS has worked perfectly ever since.

 

[glen]

Repairing sensors

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

 

[solarman216]

I would disconnect the lot, what on earth do you want ABS for any way, and at those prices!!!! waste of space, but then I do not have air bags either, all disconnected, I drive knowing that if I hit something its gonna hurt, not I will be OK cos I have ABS/air bags/side impact protection/seat belts/super this and super that, drive within the road conditions and your ability, simple, what has just bought this on, well I am up in Birmingham at the mo, and they are all raving nutters, I have loads of cars on my tailgate at 35 in a 30 camera road works zone and narrow winding lanes and trucks trying to overtake, it seems the average here is, no time for anything just move as fast as you can in a road system that changes from 3 lanes to one in 50 yards and woe betide you if, cos you cannot seethe direction signs, you are in the wrong lane, mad, but I have slowed them down, they should save all that stuff, for the banger track like I do, but not on public roads, Rick

 

[The Patrolman]

If you need ABS your tyres are crap and you cant drive!!

 

[theron]

If you have ABS fitted then it must work in order to pass an MOT - whether you agree with or not doesn't matter. If you have a crash with non working ABS and the police or your insurance company decide that it contributed to you not avoiding the crash then you could find yourself in a world of trouble.

As for whether ABS is better - are you able to control the braking on each wheel independantly with just one brake pedal?

Without ABS car manufacturers bias the braking massively towards the front brakes (~90%) so that when you stamp on the brakes the fronts will lock but the rears will not. This increases braking distances because the rear is not braking as well as it could. If the rear wheels lock when braking hard around a corner then a spin is not far away.

With ABS fitted the rear wheels will not lock and so manufacturers do not have to have such a large bias towards the front brakes and can put more force into the rear brakes - this means the rear brakes will work harder in most braking situations and improve maximum stopping power.

The biggest advantage of ABS is in a panic situation (like a kid running out from behind a parked car) where you do not have the time to perform perfect threshold braking and just have to react as quickly as possible.

Finally it not about whether you need good tyres OR ABS - You can combine good safe driving WITH good tyres AND working ABS to maximise your chances of surviving Birmingham rush hour traffic !

 

[R1cho]

You can combine good safe driving WITH good tyres AND working ABS to maximise your chances of surviving Birmingham rush hour traffic !

and that is a nightmare on the way out to the a38 from the centre, they really should change their road layouts lol

 

[solarman216]

Yes I came of that round about intending to get on the A38(M) today pulling across 4 lanes of traffic to the right I was not impressed so missed it and had to do a detour down to next roundabout come back up and do it again but this time knew what was ahead, so what was the problem, the problem was I was keeping up with all the other traffic, most of whom I guess knew the layout, had we all been going a little slower then there would not have been a problem as I would have had time to read the signs, (that are very poor) and got into the correct lane, but the point is about ABS, it is totally useless to those that drive within their skill and and the vehicles capability, I have had ABS on many cars and light trucks, I have done well over a Million miles and apart from when I deliberately tested ABS it has never activated while driving, there is a golden rule that I follow, "you should always drive at (or below) a speed that you can stop in the distance that you can see to be clear " hence there is no such thing as a "blind bend" if you cannot stop you are going too fast, Rick

 

[lacroupade]

Well you're lucky nobody has ever run out in front of you aren't you :augie

We can all drive as safely as we like, but too many accidents are someone else's fault and as Theron says, in the event of something happening, someone who had disabled safety systems would get the book thrown at them as well as losing any credibility as regards their insurer.

 

[mully]

Thanks for all your replies it was a broken wire behind the intercooler in the wiring loom where it T"s onto the bulkhead all seems well at present.

 

[spudd]

Thanks for all your replies it was a broken wire behind the intercooler in the wiring loom where it T"s onto the bulkhead all seems well at present.

Which wire was it. i have my intercooler off at the mo so opened the loom across bulkhead. i dont have a blue and pink twisted together as mentioned. any help please.

neil

 

[solarman216]

well yes I have had kids run out in front of me, but with anticipation and observation, reading the road ahead at all times , have not hit any yet, the only thing that defeated be was a hard object crashing through my truck windscreen knocking me out, ABS would not have helped there either, and incidentally had I been wearing a seat belt I would not be here today, Rick

 

[spudd]

Thanks for all your replies it was a broken wire behind the intercooler in the wiring loom where it T"s onto the bulkhead all seems well at present.

Has anyone got an idea which colour wire has broken. i havent got a blue and pink wire in my 02 loom.