Yellow ace light on and speedo stopped working

Hi everyone, don't know if anyone can help me with this one, my '99 Discovery TD5, for the last 6 months or so every now and then the yellow ACE light comes on and the speedo drops to zero, a few seconds later and the speedo goes back up but the ACE light stays on until the ignition is switched off. On starting again ACE light goes off as normal and everything fine until the next time. Seems to happen going into a dip or over a rise in the road at any speed, has happened on exactly the same spot on one road i use 2 or 3 times. Until last night it did'nt bother me but now ACE light is on all the time and no speedo at all. ACE light does its sequence when turning ignition on, red to yellow, off but then comes back on yellow. No fluid loss from ACE system, pump seems to be working and still nice and firm to drive. Have'nt had chance to get it on Autologic and my mates Testbook not working, but plugged in one of our boxes at work (Swedish made AutoCom), reads everything really well but does'nt find SLABS ecu, only body control module which does'nt incorporate ACE. Thought maybe ABS sensor for speedo but no fault codes at all. I can actuate everything on the dash using this kit and the speedo does go up. I know it'll have to go on Autologic or Testbook but just wondered if anybody has had the same fault? Have spoken to a Landrover specialist and they've never heard of these 2 faults linked together. Any help greatly appreciated!

These two faults could be linked together cos SLABS ECU is involved in both systems... the speedometer gets signal direclty from the SLABS ECU... the ACE has his own ECU which comunicates with the SLABS ECU aswell.... another fact is that these ECU's are at the same place(with the BCU, behind the glovebox) and water ingress in that area is quite common... this is the first to check.

The fact that the speedo works well on circuit test it means at least the gauge is OK. A sensor at fault usually goes together with the 3 amigos ...so let's forget about this for the time being.


Some quotes from RAVE, maybe it helps :

ACE ..........
A road speed signal is transmitted to the ACE ECU as a pulsed digital signal from the Self-levelling/Anti-lock Braking System (SLABS) ECU. The road speed signal is used by the ACE ECU for on and off-road roll compensation.

SPEEDOMETER ........
The Self Levelling and Anti-Lock Brake System (SLABS) ECU provides the signal input for the road speed.

The road speed output used by both systems(ACE and Speedometer) is on pin 3 / C0504 of the SLABS ECU( the largest connector of it, it has 18 pins...the second from left as u look toward the connectors) this signal splits in header C0290 whick is in the compartment under the steering wheel but it's hidden in a harness and quite hard to access

Disconnect battery and check for water ingress and the plugs at the SLABS ECU first...if everything is OK there we'll speak again.

It seems my insomnia is good for something though:frusty:

Thankyou very much Sierrafery, thats the best info i've been given, water ingress is quite likely as the front sunroof does leak from time to time, will check this out as soon as possible, also thanks for the explanation on how it works and how the faults are likely connected. I have found today that the offside front wheel bearing is noisy (can't hear it driving at all!) and has slight play so will get that sorted which will eliminate any ABS sensor issue. Have tested all 4 today and have good signal from all but have to fit new bearing whatever. Will be in touch either way, and oh, do yourself a favour and get your remap done, you'll love it! Only got stage 1 (plus a bit) done with Alive Tuning but what a difference! Anyway, thanks again.

TD5ilver said:

Thankyou very much Sierrafery, thats the best info i've been given, water ingress is quite likely as the front sunroof does leak from time to time, will check this out as soon as possible, also thanks for the explanation on how it works and how the faults are likely connected. I have found today that the offside front wheel bearing is noisy (can't hear it driving at all!) and has slight play so will get that sorted which will eliminate any ABS sensor issue. Have tested all 4 today and have good signal from all but have to fit new bearing whatever. Will be in touch either way, and oh, do yourself a favour and get your remap done, you'll love it! Only got stage 1 (plus a bit) done with Alive Tuning but what a difference! Anyway, thanks again.

Click to expand...

Unfortunately u will not be able to replace just the bearing... only the whole wheel hub(which usually comes with a sensor too and it's not cheap at all) ... as i said, sensor faults are always coming together with the 3 amigos. If your sensors are good leave the original sensor there and keep the new one as a spare(there is an explanation for that). I wish i could do a remap but i dont have acces to it around here.

Hi, yeah i know it comes as a complete hub, have fitted a couple to customers vehicles, cheapest i can get is £160 which i'm quite pleased with. Why do you say to use the old sensor? As far as getting your remap done, Alive Tuning will do it by post, as long as you can manage without your vehicle for a few days. They do it for customers all over the world. Speak soon, cheers.

TD5ilver said:

...Why do you say to use the old sensor?

Click to expand...

Cos it seems your ABS system is well "balanced" now as long as u have a worn hub and no 3 amigos. The 3 amigos used to come on even if no fault is present just the system gets too sensitive. The sensors to work must have an internal resistance between 950 and 1100 ohm... usually the same brand sensors have similar resistances and that makes the system to be well balanced.... putting a new, eventually different brand sensor(which's resistance is in range but might be different than the old one's) u take the risk to make your system more sensitive and get the 3 amigos more often without any serious reason(it's not 100% certain this will happen but why disturb something functional as long as it works well?) .......... ufffff, it's hard for me in english that's why i wanted to avoid that

Hi, this is aimed at Sierrafery, have had glovebox out and found 3 boxes/ecus, not sure which one is SLABS ecu, big alloy one, and 2 alongside it on left hand side. Can't find a plug with 18 connectors, have had them all off all 3 boxes and checked for corrosion, nothing found at all. Of course this might be because i'm looking in the wrong place or possible corrosion inside boxes? If you can tell me exactly which box it is please, would really like to check that one properly. It has to be something like a bad connection because the light goes off and speedo works really sporadically now, one minute its working the next its not. GRRRR!! Have done wheel bearing and that has'nt cured it, did'nt think it would, so, if you can help it will be greatly appreciated. Speak soon, thanks.

There are 3 ECU's behind the glovebox: ACE ECU- smaller, 1 connector, BCU - 4 connectors + 1 aside, SLABS ECU - 5 connectors. Concentrate on PIN 3 of C0504, see the pic below and u'll understand, looks like this http://www.ebay.co.uk/itm/Land-Rove...arts_Vehicles_CarParts_SM&hash=item4ab1e7903d




the road speed output signal splits in header C0290, which is embeded in the harness, and in connector C0067 near the steering column(there's an orange,, a white and two black connectors in line, the black from the middle) there could be a bad contact again. Dont' u have RAVE?... cos it's easyer for me to tell u where to look to see the pics

Hi, thankyou for that, i do have RAVE now, downloaded it yesterday, as soon as i get time i will check the output at terminal 3 and have found that the input on the ACE ecu is terminal 5, will let you know how i get on. Thanks again.

the input on any terminal of the ACE will not affect the speedometer though