ABS, DSC/Traction, Brake fault lights and strange braking behaviour

[canada911]

Hi guys,

A couple of weeks ago my LR3 2006 has started have intermittent fault and this is now steady (as soon as I turn the key):
1- The following amber fault lights are steady on: ABS, DSC/Traction and Brakes.
2- When I brake for a stop I hear an electrical signal in the engine bay around the ABS module and then I feal and hear the ABS kicking-in but this is bearly noticeable... This even if there are absolutly no reason for the ABS to kick-in...

Following those issues I did (in an attempt to fix the issue):
- Battery was tested perfectly fine
- Changed the brake switch for a new one
- Changed all (4x) brake lights for Land Rover new ones
- Tested the continuity of the brake pad wear seasor circuit at the cluster. all good.
- MASS air sensor is perfectly clean
- Tested almost all wire continuity of the ABS module (except HDC relays, Yaw sensor, ABS sensors, park-brake switch)
- Tested continuity of circuit between Cluster, ABS and Tranfer box control module

Due to those errors, the suspension eventually drops and suspension amber fault goes on, but I believe this is just a side effect. So for now I have removed fuse 26 to be able to drive at normal height...


I am now out of ideas... All this looks like related to the ABS or traction control units but I dont know how I can perform more tests...

Any ideas please??? Thanks!!

 

[tlt]

Check your brake light switch install, be sure you have a good connection. It could also be a bad ground somewhere, but still sounds like a brake light switch or bad ground.

Could be a wiring issue as well, hopefully bbyer will be along soon, he's the master electrical guy.

 

[bbyer]

Nav with 4x4 display?

You have made a good first attempt at figuring out what is wrong. I assume you have backed up to a reflective glass window somewhere and made certain the correct filaments are illuminating; also the front signal light bulbs are in the same circuit - changed them lately? What about the two little door side marker flashers - no LEDs in there hopefully. Also the filaments stand up and down on correctly installed genuine bulbs.

There are two brake wear sensors - front left and rear right. If still showing amber, I would be suspicious of some sort of internal breakage. The two sensors are joined together in series to feed the light, or more correctly to feed the computer that feeds the amber light. The LR documents say with worn pads, the light goes on with an open circuit and you should also get a chime for the wear indicator as well.

I had to replace a sensor even though it was new when new pads were installed. A few months later with the pads still effectively brand new, the rear sensor gave out and the amber light went on. Other than the light and the chiming, there was no suspension collapse however.

What I am getting at is that if you know where the brake wear sensor cable electrical connectors are, (both hard to get at up under the wheel wells), disconnect them and jump the two pins on the vehicle side and the light should go out.

Do you have the Nav display? If so, call up the 4x4 display and drive around with it showing.

You will be watching for odd behaviour of the suspension. If you have pulled F26E, the display probably will not react, hence put the fuse back in and hopefully the suspension will last for a few minutes.

Find a **** like a city curb and climb the curb one wheel at a time. You should have movement of each wheel separately. The reality is that on the average paved road, normal wheel movement shows very little, hence you will first want to know if each corner is displaying.

Once you know that, then you tend to watch for one corner sort of frozen or one corner going crazy for no reason.

My hope is one of the wheel height sensors is bad. If so, the fix is easy, or it could be the conductors to a wheel sensor, a not so easy fix.

Also is your wheel alignment good? If the steering wheel is crooked when the truck is on a straight road, the steering wheel sensor tells the anti skid computers the truck is turning; the yaw sensors tell the computers the truck is not turning; the computer chooses safe mode and that is down to the stops.

I will think about this some more. Generally the fix is relatively easy; finding the problem, near impossible.

 

[Houm_WA]

I've had bad wheel angle sensors before that either needed replaced or re-cal'd. The symptoms were similar.

 

[bbyer]

tyre sawed thru the wheel sensor cables

I've had bad wheel angle sensors before that either needed replaced or re-cal'd. The symptoms were similar.

About the only real time I have been down on the stops, (and that is not very pleasant), was about two weeks after I had my dealer replace the front wheel sensors.

They did not properly tie the cable to the left front wheel sensor back to the frame tight enough and my stock sized front tire over the two weeks or so, rubbed thru the cable. It appears that when turning, the rubber contacted the cable and eventually cut it.

The dealer repaired the cable, tied it back properly and all was well. The first indication of the problem was red suspension lights and then later a dropping to the stops.

Other than that, it has just been red lights and nasty messages usually related to the brake light switch, a tail light bulb or as you said, the steering wheel angle sensor. In that case, it was not the sensor, but the wheel alignment itself being out.

 

[Houm_WA]

bbyer are you talking wheel ANGLE sensors or HEIGHT sensors?

 

[bbyer]

both, so to speak

When the sensor signals from the steering wheel angle sensor are at odds with the anti skid system yaw sensors, then the suspension system can drop to the stops.

The same result can happen, that is the suspension drops, also when there is a problem with the wheel height sensors.

Our problem is that difficulty as detected by either the steering wheel sensor or the wheel height sensors can both have the same results; the 3 sitting on the stops.

When it is the steering wheel sensor detecting trouble, and the 3 drops, there is nothing wrong with the air suspension system; it is following instructions and doing what it is supposed to do, saving LR from a potential liability claim. Additionally, the fix is not suspension system related, but in this case steering system related, ie, a wheel alignment.

When the system drops due to a wheel height sensor fault, the system is still doing what it is supposed to do, that is protect LR from a potential liability claim, however the fix will be suspension system related.

As usual, our problem is to figure out in which system the difficulty lies, and not be misled by it manifestation.

 

[Houm_WA]

So....are we talking about the same wire bundle then? Does the one that is tied to the frame in the wheel well on the driver's side contain wires for both the height sensor(s) AND the wheel angle sensors?

 

[bbyer]

wheel angle sensor is mounted to steering column

The link below is to a 17 page pdf related to the traction and anti skid systems. On page 5 is a description of the operation of the steering angle sensor and how its output ties to the air suspension via the second set of contacts on the brake light switch.

All the wiring for such is inside so to speak; only the height sensor wiring and connectors are outside where it get cut by the tyres or soaked by the wet.

http://bit.ly/1kTq7Vw