Strange Traction Control behaviour

I recently carried out the SVS pack rewiring fix to address the 3 amigos. This is the third disco that I've done this repair on (the other two are still working perfectly) and the amigos have indeed gone.
The TC/ABS/HD lights come on with the ignition and go off when the engine starts, just as they should.....but, I've noticed that the TC light no longer comes on when the traction control is working (although you can still hear the Wabco unit working) and it feels like the brake is being applied a split second later. It all feels very odd! ABS still works perfectly. I guess I should get myself a fault code reader to see if anything else is logged in the ECU......

and while I was having that thought I ordered an iCarsoft i930 to see exactly what's going on inside those electronic boxes............

Mike Jones said:

and while I was having that thought I ordered an iCarsoft i930 to see exactly what's going on inside those electronic boxes............

Click to expand...

better cancel that order icarsoft doesnt communicate with td5
iCarsoft i930 diagnostic tool for Land Rover Jaguar and Range Rover Vehicles - scantool-direct.co.uk

johnlad said:

better cancel that order icarsoft doesnt communicate with td5
iCarsoft i930 diagnostic tool for Land Rover Jaguar and Range Rover Vehicles - scantool-direct.co.uk

Click to expand...

Not according to all ebay listings. They all say it talks to the Td5.......mind you, I don't want to diagnose the engine anyway.

Mike - keep me posted on this. I've got an i930 too. I recently fired off an email with pics to Ribble Valley 4x4 (where I bought mine) so they can forward it to Terrafirma, because the unit doesn't give live engine data.

HOWEVER. it does of course talk to the ABS and SLS (should you have it) and a couple of other things....

One weird thing - within the ABS data streams you can select engine speed: Lo & behold, live display of rpm! So if it can interrogate data in that menu why not in others? I'm waiting for Terrafirma to get their finger out. China (where everything of this ilk is made, should have reverse engineered a nanocom or Hawkeye by now! I said as much in my email - I hope RV4x4 don't lose it in translation

DIFFLOCK66 said:

Mike - keep me posted on this. I've got an i930 too. I recently fired off an email with pics to Ribble Valley 4x4 (where I bought mine) so they can forward it to Terrafirma, because the unit doesn't give live engine data.

HOWEVER. it does of course talk to the ABS and SLS (should you have it) and a couple of other things....

One weird thing - within the ABS data streams you can select engine speed: Lo & behold, live display of rpm! So if it can interrogate data in that menu why not in others? I'm waiting for Terrafirma to get their finger out. China (where everything of this ilk is made, should have reverse engineered a nanocom or Hawkeye by now! I said as much in my email - I hope RV4x4 don't lose it in translation

Click to expand...

Guess what happened on the way home on the day I ordered the i930.... after weeks with nothing the 3 amigos returned and stayed on no matter what I did!!

The i930 arrived Saturday morning and I plugged it in straight away. It was showing 3 faults related to SVS, so I cleared them because I knew at least 2 of them were related to me messing about with the plugs last week. I thought if I cleared them then the true fault would come back. The 3 amigos disappeared and have not been seen again since. Odd.

What I did find while looking at the live data on the ABS is that I have one shuttle valve closed even at idle, so it looks like I have a stuck valve (SVS pack was already replaced) because I'm pretty sure they should be open when nothing is going on. I guess this would explain the lack of traction control. I took it up a local lane to test on Saturday night and proved that the TC is not working at all. No TC light, no sound from the modulator and one wheel spinning.........still no amigos though.

I'll have to get back to you regarding live engine data as I only checked for engine fault codes (and found 4). I did see the rpm displaying correctly while looking at the ABS live data screens, and it seemed to show the ABS sensors reading correctly when I took it round the block.

Looks like it might be time to consider either a used modulator or bite the bullet and buy the new valve block............

Just plugged the i930 into my mate's D2. As I thought, both switches open as the default position, so I have a stuck valve............or a faulty new SVS pack...........

When you say SVS pack - do you mean the wires in a black plastic surround which bolts on to the bottom of the ABS unit? If so, then yes it may be faulty. However, carry out the SVS wiring mod.

Cheers, Mike. :tea:

DIFFLOCK66 said:

When you say SVS pack - do you mean the wires in a black plastic surround which bolts on to the bottom of the ABS unit? If so, then yes it may be faulty. However, carry out the SVS wiring mod.

Cheers, Mike. :tea:

Click to expand...

Yes, I replaced that AND did the wiring mod at the same time. THis is the 3rd Disco I've done this mod on and the only one that I've had issues with afterwards. I tested the switches and wiring before fitting and got the desired 3k Ohms both open, 2k Ohms either one closed, 1k Ohms both closed. So, either the new switch pack developed a fault after fitting or a valve in the modulator has got stuck.

...er hit it with a hammer? Out of ideas.. is there a way of testing the Wabco unit itself? Mechanically I mean?

DIFFLOCK66 said:

...er hit it with a hammer? Out of ideas.. is there a way of testing the Wabco unit itself? Mechanically I mean?

Click to expand...

I guess if I drop the SVS switch pack again and retest the resistance that will prove one thing or the other. It is odd that it was working OK before I replaced the switches, other than having the intermittent amigos.

DIFFLOCK66 said:

Mike - keep me posted on this. I've got an i930 too. I recently fired off an email with pics to Ribble Valley 4x4 (where I bought mine) so they can forward it to Terrafirma, because the unit doesn't give live engine data.

Click to expand...

I tried it last night and can confirm that live engine data does not display correctly via the engine menu. I got 4750rpm while at idle with 4 cylinders showing 0 and number 3 showing 12rpm.......
It does appear to show engine fault codes correctly though.

Fixed it!
As mentioned earlier, the i930 was showing one SVS switch closed with no brake pedal pressure applied. With the i930 in view and the display showing the SVS switch positions, I dropped the SVS switch pack from the bottom of the modulator. As soon as I started dropping the switch pack the display went from one closed to both open. I put the screws back in and pressed the brake pedal, both closed. As I let the pedal back up it again showed one switch closed.
I dropped the switch pack out again and confirmed the switches weren't sticking, so I compared it to the old switch pack. The problem was immediately noticeable. On one of the switches the rubber gaiter was not seated correctly. It was too high up the switch and must have been getting stuck in the modulator when fitted. I gently pulled it into the correct position and refitted the switch pack. Bingo! Both open with no pedal pressure.
I took a quick trip down our local lane to get one wheel off the ground and hey presto, TC light on, lots of noise from the modulator and I didn't get stuck. Yay!

SWEET! Glad it got solved!