Thread: TD5 Conversion - SLABS speedo signal

Mick, D2 uses left front ABS for signal, no transfer case transponder, its the pink and green wire coming out of the grey plug on the wabco ecu.Well it is on the one I have. Cut this wire and run it to you true speed and back.

SLABS draws speeds from all 4 wheels and then generates an average speed from that, keeping in mind it is the ABS/ETC computer? It will still generate speed frequencies with reduced numbers of working sensors though but of course throws fault codes and 3 dash lights if this is the case (see 3 amigos) but in you case these may not be connected. The frequency generated starts with a baseline diagnostic 1hz and then as speed increases the frequency increases. If the 1hz signal is not going through it may fault, but I don't recall which computer throws faults.

It would be interesting to know how the Defender has done it, which may be an simple setup.

Originally Posted by Slunnie

SLABS draws speeds from all 4 wheels and then generates an average speed from that, keeping in mind it is the ABS/ETC computer? It will still generate speed frequencies with reduced numbers of working sensors though but of course throws fault codes and 3 dash lights if this is the case (see 3 amigos) but in you case these may not be connected. The frequency generated starts with a baseline diagnostic 1hz and then as speed increases the frequency increases. If the 1hz signal is not going through it may fault, but I don't recall which computer throws faults.

It would be interesting to know how the Defender has done it, which may be an simple setup.

According to the D2 RAVE the Vehicle Speed Signal is as follows:

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.

How did you go with this Mick?

I am close to a similar setup on my Defender (D2 TD5 and Auto swap)

I too will have the same issue re: speed input.
So far I know: The Auto has its own output shaft speed sensor to talk to the Engine ECU for shift point vs engine RPM, this input wont work for the speedo as it doesn't represent anything other than trans output shaft speed. So no good for Speedo, Cruise or SLS

The input signal required is a sine wave at 8000 pulse/mile as Paul has said from the ABS wheels sensors.
The SLABS ECU needs a valid speed signal to
1/ Provide Speedometer reading
2/ Cruise control function & SLS
3/ Allow the Auto ECU to differentiate/ select High and low range maps in conjunction with the Hi/Lo input switch. necessary to allow or prevent TC lock up etc according to configuration selected.
4/ compare road speed/ Engine speed/ Transmission/shaft speed for ABS and TC

I have found the TD5 Defender has speedo encoder/ sensor which fits directly into the TC output housing (D1 and Defer TC housing are the same but the D1 encoder is different)

The TD5 Defer encoder ouput is a square wave with 4000 pulse/mile output.
However, when it reaches the TD5 Defer speedo it is doubled to 8000 pulse/mile output signal to the engine ECU. (sounds like the signal we need)

So the ability to modify the signal already exists at the correct frequency. What I haven't yet confirmed is if it remains as a square wave signal or modifies this to a sine wave as a suitable input to SLABS ECU. With an appropriate signal I was going to use that at all 4 SLABS signal inputs.

In any case a TD5 Defer encoder with a modulator to convert the 4000 pulse/mile square wave signal to 8000 pulse/mile sine wave signal should be relatively easy based on my interweb searches especially as LR already have the circuit to do at least half it.

What I have done and it is working is get of some abs sensors off a RRC/D1 as my hubs already had the ABS slots I just had to re-install them. The plugs on a RRC/D1 abs sensor are the same as a D2 ABS sensor so it just worked. I got lucky! Only the rear wheels are working for the moment and I have a functioning speedo. The fronts get a little more complicated as I blew the old weak ABS CVs a long time ago and at the time retro fitted the older 2 part stronger CVs form a late 80's RRC. To get around this I ordered a few 60 tooth ABS reluctor rings for a Freelander from a guy I found on ebay. I will then have to machine down my CV's a few mm and press fit the rings on to get the front 2 wheels working.

As a bonus I will get 4 wheel sensors which will give me access to ABS and traction systems on the D2 once i plumb the brake modulator back in.

You might have an issue with the TD5 Defender transponder as it might only be x1 signal. The SLABS on a D2 looks for x4. If you have or get hold of ABS hubs for Yr Defender then this could would work for you also. I was able to turn off HDC and TRC with my Nanocomm but still have a dash that looks like a xmas tree. I think until all 4 speed sensors are working the SLABS ECU things something is wrong and will throw out warnings.

HTH

Mick

Thanks Mick, that should sort me then.
I couldn't find much the info on the D1 sensors, but to be honest, didnt think enough about retro fitting them to the Defer front housings so went researching the other options.
I have the Cvs with reluctor rings, so I'll just install/retro the D1 front sensors I have lying around.
My plan was to have one output "common" to all 4 SLABS inputs, but I'll hook up the 2 from the front now and " common those to the remaining 2 inputs. (may not like it)
ABS on the Defer wont be happening so along with TC and HDC wont be an issue for me.
Appreciate your help.

Originally Posted by strangy

Thanks Mick, that should sort me then.
I couldn't find much the info on the D1 sensors, but to be honest, didnt think enough about retro fitting them to the Defer front housings so went researching the other options.
I have the Cvs with reluctor rings, so I'll just install/retro the D1 front sensors I have lying around.
My plan was to have one output "common" to all 4 SLABS inputs, but I'll hook up the 2 from the front now and " common those to the remaining 2 inputs. (may not like it)
ABS on the Defer wont be happening so along with TC and HDC wont be an issue for me.
Appreciate your help.

Cool if you have the sensors and somewhere to put them then you should be ok. let me know how you go with the "common" wiring. its plan B for me if the ABS rings wont work. All i know is that the SLABS knows that each sensor is plugged/missing so doubling them up might confuse it as it got twice as much signal or 1/2 much voltage...

Mick

Originally Posted by disco_ute

..... let me know how you go with the "common" wiring. its plan B for me if the ABS rings wont work.
Mick

Will do, though I suspect at my current rate of progress you will be on top of it before me.