Land Rover Repair: Discovery II 3 Amigos, air gap, abs sensor

Question
Hello John:

I am an engineer who likes to trouble shoot problems and doesn't like to get ripped off from dealers.
 
I am having the 3 Amigos problem with my 2000 Discovery II.  The 3 lights come on a lot when it rains and sometimes during normal conditions or parking lots.  They go off after the car sits for awhile and it's dry.  I just changed the rotors and pads this past weekend.  I didn't use Land Rovers parts.  I inspected the ABS sensors as best I could and didn't see any physical damage t the wiring.  I tried removing the ABS sensor for inspection and cleaning without success, I didn't want to put to much force on it and break something.

You mentioned an ABS ring in an email sent to another Disco II writer.  Could you elaborate how do I check the ABS ring and remove the ABS sensor?  I think the problem is related to the sensors or wiring, considering the lights come on in wet conditions.  Do you have any other ideas for me?  I finally scheduled a diagnostic visit with Land Rover to see if they can track down this problem.  

Thanks you,

Garry


Answer
Hi Garry,

ahh yes...the ABS exciter ring...  I believe they are inside the swivel pin housing and very difficult to work with.  

There are two things you could do from your own garage (base on owners comments)...

With an multimeter:

Sensor check:

1. Carry out multimeter test, check electrical resistance of sensor, this should be 700-2000 ohms. Check sensor voltage output, this should be greater than or equal to 0.93 VAC RMS when rotating the wheel at 1 rev/sec.

2. Check sensor air gap. Push sensor through bush until it touches exciter ring. Sensor will be knocked back to correct position when the vehicle is driven.

3. Check run out of the exciter ring and rectify if necessary.

4. Check bearing play and adjust if necessary.

5. Check sensor bush and exchange if necessary.

Re-seat ABS sensor:

the ABS sensors are internal, that is, the reluctor ring is inside the swivel pin housing. The sensors can be a bit tricky, as they are simply a push fit in the top and they can be dislodged - either by you or by brush or branches on the trail. Push it home - it'll reset to the proper spacing with a turn or two of the wheel.

I hope this helps,

JohnMc