Hi all I have taken delivery of my 2004 Discovery II, all is well except the speedo and forward sunroof.

Sunroof simply does no open but no leaks - 18 hours of constant rain so pretty confident both sun roofs are ok.

The speedo however has a mind of it's own, when working it is perfect matches up with my GPS with in a KPH at any rate. But over the 50 or so K drive home it often dropped to and stayed at zero or bounced around a bit between zero and around 10kph mark, then popped back up.

I have to do a test with my tablet to confirm the ECU readings while driving, but at this point I am leaning towards a connector issue, as there are no stored codes showing with a standard code reader.

I have done some research but have not found a definitive answer to how the speedo is driven.

If I follow correctly the speedo is driven via the SLABS, which receives singles from the ABS speed sensors and a sensor on the transmission.


Update

After some more driving and observation : this condition seems to occur when I come off the gas and brake, the speedo will bottom out sometimes bounce and then recover or stay at zero. Brakes were done by the dealership before they sold it, there may be a related issue there.

All braking functions are good with no issues.

If either the sensor links fail I would expect a code to be thrown, can anyone confirm if I am correct and a general troubleshooting procedure.

Solution

After reading a great deal about speed sensors and the SLABS I took the simple approach of verifying the connectors were all seated firmly in to the SLABS itself. 4 hours of driving in stop and go city traffic (one very hard brake) and highway and the speedo has stayed functional. It would appear to have been a loose connection. Fingers crossed it stays happy.