It a Wabco thing, the ECU stops communicating over 5mph.

Anyway, I've spent today on the car and thought I was going to declare Bolt the winner. But not.....

It needs an MoT and one thing I had noticed was that the RH front axle oil seal was leaking. Not a specific MoT fail I don't think, but I know the tester wouldn't be impressed so, ignoring the ABS for the time being, I set about changing that, It was pretty obvious that the hub had been out before and the dust shield around the ABS ring had been slotted rather than just having a hole so the ABS sensor doesn't need to be removed. Got the hub out and turning the hub it felt a bit like a worn bearing but didn't, if you know what I mean. I realised it was the ABS ring rubbing on something and then noticed this

a dent in the dust shield. Had a closer look at the ring and noticed some teeth had bits of rust on them

While others had almost merged into one with general crud

So, could it be that due to this the signal from the sensor was getting corrupted at higher speeds resulting in brakes that worked perfectly at low speed but the ABS was kicking in at higher speeds? Cleaned it all out and carried on with the job I had started. As I had suspicions about the brake light switch, I'd got a new, genuine one of those just to rule it out so fitted that too. Once all back together I took it for a test run.

ABS light goes out at 5 mph, no faults shown on the dash so apply the brakes at about 15mph, perfect. Go a bit faster and applying the brakes at 25mph, the ABS can be heard and felt operating just as before. As another test, as the RH rear sensor was such a nice fit I could pull it out with my fingers, I managed to get my arm down behind the wheel and pulled the sensor out. As soon as I started moving the dash beeped and came up with ABS Fault and Traction Failure, as you would expect when it doesn't see normal rotation on all 4 wheels. Drove off down the road, tried the brakes at 25mph and the ABS kicked in just as before. But, with a detected ABS fault, the ABS would normally be turned off? Shoved the RH rear sensor back in, drove a little further to confirm that everything was now back to normal and the fault message was no longer there. Then opened the bonnet and pulled fuse 38 that feeds the ABS ECU. Started up and got an immediate ABS Fault on the dash, drove off and applied the brakes at 25mph, perfect at 40mph, perfect and at 50mph still perfect.

This now all seems to point towards the ECU applying the ABS when it doesn't, and shouldn't, need to. It shouldn't do anything when it has detected a fault (or at least the earlier Wabco C doesn't, my other half used the Ascot with one duff wheel sensor, a dash full of warning lights and brakes that worked perfectly for 3 months last year) but it is doing. However, when I called my local tame dismantler (Avenger 4x4), the response when I asked if he had SRD100500 or 501 on the shelf, his reply was simply, rocking horse manure.....

There's a couple on eBay at the moment but not cheap and although the owner wants it sorting and is quite happy to pay £200 for an ECU, I'm not one to just throw bits at a car and hope they fix it, I want to know it will fix it first. However, I should have the opportunity to borrow one next week so will know once and for all.

As for the MoT, it's booked in tomorrow morning. As the brake test will be done at low speed with the deccelerometer, I'm hoping the tester doesn't go fast enough to notice.....

Thanks, didn't realise you were on here too Lefty.

Up to £1126 at the moment so has gone beyond the original target of a grand. Still got just under two months to go before the jump date of 22 April so no idea what it will get up to by then.

Exactly what I saw on both the inlet and outlet valves. That would make sense when the brakes aren't applied but I would have expected them to change when the brake pedal is pressed. Nanocom document says:

• Inlet valve: This shows the voltage being applied to this valve by the ABS ECU. When driven the
voltage should be around 2.8 to 3.6 Volts and when not being driven should be around 0 to 0.5 Volts.
• Outlet valve: This shows the voltage being applied to this valve by the ABS ECU. When driven the
voltage should be around 2.8 to 3.6 Volts and when not being driven should be around 0 to 0.5 Volts.

and I'm assuming the valves will be driven when the brakes are applied......

Thanks Leo, I'll check that but as both are switching I suspect that isn't the problem. Can you check the inlet and outlet voltages when the brakes are applied for me please? I would have thought the voltage should change when the brakes are applied but they aren't doing.

Latest update is that I suggested to the owner that he pulled Fuse 38 and tried it. Despite having the ABS and TC lights on permanently, the brakes are working perfectly....

No afraid I don't, all I've got is a graphical multimeter which would be able to show one sensor but with a lot of messing around swapping from one to another. Not only that, if the sensors were reporting differing speeds, I would expect it to bring up an ABS fault on the dash and log a fault too.

A scope is one of those things that I wish I had once or twice a year but I was spoilt when working with having £40k+ worth of high quality test equipment as personal issue so the affordable stuff always seems inferior to what I got used to using.

The car is coming back to me on Monday so it might be too late. However, the readings I want to know is whether the two brake light switches should both be the same (both open and then both closed when the brake pedal is pressed) or if they should swap over so one open and one closed as on my GEMS. There are also screens showing Inlet and outlet valve voltages. These are all at 0.00V (with the occasional 0.06V showing intermittently) but do not change when the brake pedal is pressed. I would have expected them to but they don't.

It's a bit of a pain that the ECU disconnects diagnostics once over about 5mph, being able to see what it is doing at speed would be very useful.

I haven't but I did think after the owner had taken it away I could have pulled the ABS fuse so it doesn't do anything. At least he'll have brakes, just no ABS or TC (and a dash full of warning lights).

I'm still a little confused by some of the readings I get on the Nanocom though. Both my cars have the earlier Wabco C system and this is Wabco D. When looking at the two brake light switch status, on the C system one is open and one is closed and they swap over when the brake pedal is pressed. On the D system they both show the same status and change from open to closed (or the other way round) when the brake pedal is pressed. That would suggest that the switches are different but the parts list shows the original part number for a C system car supersedes to the same one as fitted to a D system car which makes me think they must be interchangeable? The inlet and outlet valve voltages not changing when the brake pedal is pressed doesn't seem right either but I need to find a D system equipped car with working brakes to stick the Nano on and see what that reads.

Nah, that's a con rod but the only time I've seen one that has done that was when a big end bearing seized. Does the bearing move? Mind you, the one I saw was on a Toyota 1ZZ-FE engine that had been burning so much oil, it ran out. Made quite a mess when the broken end came out the side of the block......

A bit more information on this problem which has had me and a recently retired Land Rover mechanic scratching our heads. I'd only been given parts of the story but have now got a full sequence of events. The ABS light was staying on and he was getting ABS and Traction faults. That was down to the ABS ring on the LH rear which was changed and the problem has been there ever since. Although his mechanic had told him he had changed sensors, they hadn't been changed but it does have a brand new accumulator and brake modulator. The shield on both front hubs has been slotted so the hub can be taken out without removing the sensor which also means you can see the ring and the end of the sensor and check the air gap. We gave both front sensors a tap with the mallet to make sure they were fully home before turning out attention to the rear.

LH rear sensor came out without too much effort and looking down the hole the ring had a lot of oil on it. Now whether this was done by whoever change the ring or the axle oil seal is leaking, I don't know but we pulled the hub out slightly to allow it to drain and cleaned it up with a liberal spray of brake cleaner. Put that back together and tried it again. Up to 25mph the brakes are perfect but over that the ABS is kicking in. Theory was that while the speed readings were fine up to 5mph when the Nano disconnected, maybe once over 25mph one sensor was reporting an incorrect speed so the ABS was kicking in then. OK, so we've done 3 out of 4, lets attack the RH rear. On this, despite them normally putting up a monumental fight, I got hold of the sensor and just pulled it out. No pliers, no wiggling, it just pulled straight out. the ring looked pretty horrible and rusted so it was cleaned up with a combination of scraping the crap out from between the teeth with a screwdriver, blasting it with brake cleaner to degrease it and finishing off with an airline. Put the sensor back in but before putting the wheel back on, tried turning the hub while I had my finger on the sensor. For 2/3rds of a turn it could feel every tooth as it went past the sensor but for the other 1/3rd of a turn, I couldn't. So it looks like that one is a bit worn or is slightly off centre (or the wheel bearing is on its way out). Took it out to see if it was any different.

Up to 25mph the brakes are fine, at around 30mph the ABS is coming on but it still stops OK but it gets really scary at 50 mph. Hit the brake pedal, the ABS can be felt working but the brakes aren't! It is only when you really stamp on the pedal that they work, but then you are into scraping your passenger off the inside of the windscreen type braking. It is almost as if, rather than releasing one wheel that it thinks is turning slower than the others, it is releasing all of them and maybe only braking on one wheel. But if it was doing that, it would pull to one side so I think releasing, or not applying, all 4 is closer to what is happening. Maybe the lack of voltage being shown on the valves is correct, rather than the Nano just not showing them, and it is an electronic problem?

I'm going to see if I can get a halfshaft with a non corroded ring and try to swap the ABS ECU for a known good one because by now, with a combined 50+ years of working on Land Rovers, it's got both of us baffled. If only we could get the Nano to connect at above 30mph we'd at least know what wheel speeds are being reported.

After all the warnings and thoughts of what could go wrong, it's almost worth doing it to see what can happen......

For leak testing AC systems I've got a bottle full of Nitrogen at 190 bar, using that could get interesting. From a safe distance anyway.

So now I've got the car here and it gets curiouser. Checked the brake light switches with the Nano and sw1 was operating before sw2 so I thought that was it. However, after pinching the brake light switch off the Ascot, fitting that and checking with the Nano and seeing both operating at the same time, a quick blast up the road revealed it was no different. At speeds up to about 25mph the brakes are fine, at anything over that, the ABS can be heard and felt through the brake pedal. ABS modulator looks to be new so bled that, but only that, and while a tiny bit of air came out, again no different. Tomorrow it's going to be a wheels off and check all the sensors and reluctor rings.

No matter how hard I tried I could not get the Nano to connect when moving so other than being able to see the individual wheel speeds at up to around 6kph, I wasn't able to check them at any higher speeds. One thing that I am confused about, not usually working on Wabco D systems, is the Inlet and Outlet valve voltages. All of them show 0.00V except at odd times one or two will jump to 0.06V. However, the Nano documentation says that this shows the voltages to the individual valves and I would have thought that with the brake pedal pressed a voltage would appear but it doesn't, they all stay at 0.00V (with the odd change to 0.06V).

Sounds like your pump is getting a bit weak but that wouldn't affect the height or the switch not working. The switch isn't just a switch, there's some electronics inside it too, so I would suspect that has died. At least you've got another you can try swapping to prove or otherwise.

If it is on High it should drop down to standard at 35 mph. Does it or does it just stay there all the time? Try using the Nano to open the exhaust valve and a couple of corner valves and see if it drops then. That will rule out the valve block and driver pack.

If you've got a press you could mount it in that but you'd need to make sure it was held flat at top and bottom so it wouldn't launch itself out at you.

That's right and it's a pretty horrible thing to happen to anyone. They think she will be paralysed down her left side so it's doubtful she'll ever be able to ride her horse again. The only fortunate thing about the whole episode is that one of the other women, a nurse, had followed her out of the stables and saw her go off the road, otherwise she could have been there for hours before anyone saw her car in the ditch.

My daughter has asked me to thank everyone she has never met for contributing.

Good point, suspension air bag or air bag? Air bag is easy, connect two (long) wires, get a safe distance away and connect to a battery. If it does nothing, it's buggered, if it does something it wasn't buggered but is now......

You'd need to rig up something to stop it blowing the ends off but it will have to be pretty strong and hold it securely. To properly test you'd need to inflate to around 75-80psi as that is what it needs to support over a half tonne (1/4 of the weight of the car).

I will, before, during and after.