Thread: Speedometer not working

I would hazard a guess, and advise that if you connected the input and output wires at the Truespeed unit, you take it out of the equation from the BCU to speedo to eliminate a dead speedo corrector as the culprit.

That's what I'd do as a first point of call.
if still no speedo readings in bypassing the Truespeed, then .... IDunnoNuthink

Slunnie has done a writeup about installing a Truespeed unit back in the day

Hope that helps.

Originally Posted by AK83

I would hazard a guess, and advise that if you connected the input and output wires at the Truespeed unit, you take it out of the equation from the BCU to speedo to eliminate a dead speedo corrector as the culprit.

That's what I'd do as a first point of call.
if still no speedo readings in bypassing the Truespeed, then .... IDunnoNuthink

Slunnie has done a writeup about installing a Truespeed unit back in the day

Hope that helps.

Thanks for the tip. I wasn't the one to install this unit - is there a simple way to bypass/troubleshoot it?

Does the SCU correct the speedo reading when changes to gearing have been made, by tyres, wheels or gears?
My D2a was supplied with 18" wheels, I subsequently fitted 16" wheels with 265-70x16 tyres, the same diameter as the stock 255-55x18. These sizes cause the Speedo to indicate ~5 km slow.

Originally Posted by V8Ian

Does the SCU correct the speedo reading when changes to gearing have been made, by tyres, wheels or gears?
My D2a was supplied with 18" wheels, I subsequently fitted 16" wheels with 265-70x16 tyres, the same diameter as the stock 255-55x18. These sizes cause the Speedo to indicate ~5 km slow.

Just tested it but driving around switching gears manually, didn't do anything on the speedo or the nanocom.

Just confirming - the SCU was fine for a good 12 months. I'm just sending it as part of the overall setup, not trying to suggest it's the root of the issue - just that it's the setup that I have.

Originally Posted by V8Ian

Does the SCU correct the speedo reading when changes to gearing have been made, by tyres, wheels or gears?
My D2a was supplied with 18" wheels, I subsequently fitted 16" wheels with 265-70x16 tyres, the same diameter as the stock 255-55x18. These sizes cause the Speedo to indicate ~5 km slow.

Yes, it does for any of them if it is an auto.

If it is a manual gearbox you will likely lose the cruise control operation unless you set the SCU to suit the new diff ratios.

Originally Posted by Artems Disco 2

Hi All!

I'm in a bit of a bind - any assistance would be appreciated. My speedo has stopped working - I've tried googling around, and have no had any luck. My disco 2 includes a speedo corrector (I didn't set it up)

located under the steering wheel. I checked that there's volts leading to the fuse box which is seems to connect to.

I've checked all the other factory fuses, I've unplugged the pinned plugs that go into the SLABS and plugged them back in.

my reader shows 0KMs when driving, and when i press "on" on the speedometer tester thing, nothing happens on the dash.

any help would be appreciated - i should also note that i've recently installed a dc-dc charger for dual lithium batteries.

i've attached relevant images
IMG_1617.jpgIMG_1616.jpgIMG_1615(1).jpgIMG_1614.jpgIMG_1612(1).jpg

First just try the 2nd speed setting on the SCU - the switch is on the side of the box. If still no good, I would also find where the SCU is wired into the Disco and replug the wires together to bypass the SCU. Then go for a drive and see what the dash and Nanocom say. Also check for any faults in the SLABS. If the Nanocom and dash are still reading 0kmh, I would then check that all of the ABS lines are still good. The SLABS computer generates a speed signal based on the information from the ABS lines, however normally if there is a problem there then the dash lights up with the 3 fault lights - check those lights all work during startup. If the lights do work on the dash, your ABS lines all look good, then I suspect you've got a SLABS computer problem going on and potentially may need to try a different one (there are quite a few variations of the same part - match the part numbers), either/or there is a break in one of the SCU plugs or wires from the SLABS to the SCU plugs or the SCU plugs into the car.

The SCU is more than likely wired into the Disco using the Green wire and the Yellow wires, and then probably spliced into the signal output wire from the SLABS computer which is Pink with a green line. The SLABS computer is found behind the front passengers kick panel in front of the door under the dash at about the passengers foot height - I would expect your SCU plugs to be down there.

I had to replace the instrument cluster with a second hand one, causing my odometer to read 50,000km higher than actual.

Originally Posted by biggin

I had to replace the instrument cluster with a second hand one, causing my odometer to read 50,000km higher than actual.

That should also make the odo flash because it is mismatched with the BCU. I'm not definate, but I thought you could correct either the dash or the BCU with a Nanocom so they match???