2 x Technical question on ABS SLABS TC - NOT 3 Amigos

Hi guys

Would like to pick some brains about the more technical aspects of SLABS on the D2

As I mentioned this is not a thread about the 3 lights on the dash!

Question 1 2000 D2


So winter in Canada is long and cold, and our local authority is getting green and not using salt any more and relying on us all having winter tyres - that's fine, but the D2 even with winter tyres is a nightmare when trying to stop for junctions and lights - so bad I pulled fuse 28 on the side of the road to stop the system working - naturally the dash is lit up like a Christmas tree. But the car now stops in 1/4 of the distance when you know how to brake on ice!

So my question is can I disable the ABS but retain the traction control - 'cos that it real handy to have

I have the Lynx system here but there are not that many SLABS options


Second question is sort of complicated but I think it may be down to a newer car

2004 D2

Converted to a 300 Tdi 5 speed from a 4.6 auto with slipped liners

Now this is not a question how to get things working as I already did a 1999 and it is working perfectly, so when I did the 2004 I followed my notes and everything works -except the TC and hill decent lights are on after the engine starts

When I put the ignition on, all the lights on the dash come on then go out as they should, but as soon as the car starts, the TC and hill decent come on - BUT the ABS light goes out and works - there are no fault codes present

Now I bought this car with no engine so I cannot say if this was a problem before, and as this transfer case had the diff lock already fitted I retained the old transfer case and electrics but fitted the regular R380 linkages instead of the cable links on the Auto box,

BUT I did read that the engine ECU talks to the SLABS on later cars - so I am wondering if I find an old SLABS ECU would that work?

Or does someone know better?

Thanks

Mike

Question 1 - Id say no. Its the same thing, kill one...kill the other. Maybe a switch? Switch the power - fuse 28- then switch it back on when you need TC.

Question 2 - traction control talks to the engine pcm to limit throttle so no engine pcm no talk

My thought were to fit a NC switch on the pedal bracket - through a 3 way switch on the dash - summer/winter driving, then into the fuse 28 (with in line fuse to protect wiring)

Or summat like that - so if in winter as soon as I hit the brake the ABS is off, then I will keep traction control as you do not use the brake when pulling away - worth a shot - lights on dash will flash on an off but better than being on all the time

As for 2 I have retained the original crank positioning sensor and machined a reluctor - rev counter is spot on, also the throttle positioning sensor is on the injector pump - maybe my readings are not in range for the later SLABS ECU - I know there was a difference but hard to find out the details

For this reason I retain the original engine ECU the PWM signal is important

I did find this info

Hill Descent Control (HDC) signal
The ECM transmits throttle angle, engine torque, engine identification (Td5 or V8), and transmission type (automatic
or manual) data to the SLABS ECU to support the Hill Descent Control system. The information is transmitted via a
0 – 12V pulse width modulated (PWM) signal at a frequency of 179.27 Hz.
Function
The HDC signal output from the ECM is via pin 29 of connector C0636. The ECM generates a PWM signal that varies
in pulse width in accordance with changing throttle angle or engine torque. The throttle angle data is transmitted on
pulses 1, 3, 5 and 37. The engine torque data is transmitted on pulses 2,4,6 and 38. The engine and transmission
information is transmitted on pulse 39. A synchronising pulse is transmitted after every 39th pulse.


Will have to grab hold of a 'scope and see what is on pin 34 of connector C0637

Thanks for the info - getting a little out of my comfort zone when it comes to electronics rather than electrics!
Mike

Hi, never let the SLABS ECU without feed fuse cos it has involvment in the engine management too, without feed for SLABS the engine ECU will miss the VSS(vehicle speed signal) which is part of the adaptive strategy also if you have SLS it will be disabled as well

ENGINE MANAGEMENT SYSTEM - TD5 said:

Vehicle Speed Signal (VSS)
The VSS is an integral part of the ECM's overall adaptive strategy. The ECM receives the signal direct from the
SLABS ECU. The SLABS ECU is not connected to the controller area network (CAN) so therefore is hard wired.
Vehicles fitted with automatic transmission have two vehicle speed input signals to the ECM. One signal is from the
SLABS ECU and the other is from the automatic transmission ECU. The ECU compares these speed signals.
The ECM also receives transfer gearbox information. This allows the ECM to take in to account the vehicle being
driven using low range gearing and compensate as necessary. The signals generated by the SLABS ECU for manual
transmission, and by the EAT ECU for automatic transmission are received by the ECM in the form of a PWM signal.
The frequency of this signal changes in accordance with road speed.
The input signal for the SLABS is measured via pin 13 of connector C0658 of the ECM. The SLABS ECU generates
a PWM signal switching between 0 and 12 volts at a frequency of 8000 pulses per mile.
For vehicles with automatic transmission the input signal for the EAT ECU is measured via pins 32 and 35 of
connector C0158 of the ECM. These pin numbers provide a bi-directional communications link using the CAN data
bus.

Click to expand...

You can trick the system if you want to as to have TC but no ABS cos ABS will work only if the SLABS gets "brakes on"signal(1 KOhm against earth) from the SVS on that yellow/green wire which is involved in "option B" SVS repair wiring mod too rather than the TC which must get "brakes off" input(3 K Ohm) to work so the gist is to splice in the SVS circuit with a switched 3KOhm resistance as to bypass the "brakes on" signal then you'll have TC all the time but no ABS as the system will not "know" when brakes are on to activate ABS mode...also no 3 amigos will show then but IMO you better not mess with the SLABS though

If you want only to inhibit the whole ABS system remove relay R10 in engine bay fusebox not the fuse then 3 amigos will be on and only mechanical braking action

None of my 3 x D2's have air suspension from the factory

So let me get this right

If I tap into the YG and fit a 3k ohm resistor via a switch to ground it would disable the ABS signal to the SLABS?

The ABS works only when the SLABS gets the "brakes on" signal from the SVS and that's 1kOhm, the ABS will not kick in as long as it gets 3kOhm(brakes off) signal so if that's what you want you must cut the YG wire and connect it through a NO/NC relay's NC contact then the system will work normally and put a 3kOhm resistor to ground on NO contact, this way if you switch on a feed to the relay's coil the SLABS will get 3kOhm input even if you push the brake cos the SVS will be bypassed and as long a s the SLABS doesnt "know" the brakes are on it will not activate ABS if you see what i mean... if you dio that make some tests in the field before you go to public places cos i don't know how the TC would react on that but in theory that's how you can stop the ABS to kick in and keep the TC in working order

I get it - so using a regular 5 pin relay

30 would be the yellow /green from the harness to the modulator
87a NC would be yellow/green back to modulator
87 NO would be through 3K ohm resistor to ground

85/85 via a dash switch

Correct?

britrest said:

I get it - so using a regular 5 pin relay

30 would be the yellow /green from the harness to the modulator
87a NC would be yellow/green back to modulator
87 NO would be through 3K ohm resistor to ground

85/85 via a dash switch

Correct?

Click to expand...

You've got it, only correction is 85 - feed from switch , 86 - ground

Sorry Typo!

Will give it a go

Many thanks

Mike

Good luck, just make tests somewhere in the wild before you go on the road to make sure it works as you want to cos what i said is based only on the theoretical operation mode of the system but it's not tested live.

He who dares wins Rodney!

Anything is better than the system at the moment - driving on 2 inch of solid ice with a D2 is fine - until you need to stop - the ABS is too sensitive

I was having a beer with a few mates last night and it seems I am not alone - a few accidents round town due to uncontrollable stops

I live on a back road here so a good testing ground, and that is why I need traction control - when the plough passes and dumps 2 feet of snow in front of the car you need that bit extra that the TC gives to pop through the snow bank from a standing start

Quick feed back as I have been a bit busy, but I did the modification and it worked - but not quite..

The TC works and no lights are on, and on the dry there is no ABS as I can see - I have not been able to find a dry long straight yet, but on the ice it gives the ABS a few kicks through the pedal - then the pedal goes a lot further down than normal, then it repeats - then you are slowing to a stop which is controllable - way better than before when you used to do sailing past a stop sign.

I have just hooked this up temporarily under the bonnet as I was stuck for time, but will test again this week