spegru

Hi not too many responses to that. However I did swap a PM with another member (who I'll keep anonymous unless he/she wants to put their hand up!) who said (among other things)

"the Mk1 Focus cluster is a Hybrid Electronic Module (HEM). It makes a more complete use of the OBD data highway, though a few indicators are still direct switch/signal. To maintain 'legacy' compatibility, the VSS signal, which is a 12v Hall Effect goes only to the PCM. The PCM conditions it to a similar 'pulse' for use with older devices such as radio volume, cruise control,etc. The signal is also conditioned into the OBD multiplex signal. On the transverse gearboxes (MTX, IB5) the VSS uses a 40 tooth wheel that replaced the older mechanical drive. So the PCM gets 40 pulses per drive wheel rotation. The PCM can be recalibrated by Ford by a small amount to allow for wheel/tyre variations. The ST170 the VSS uses the Crown wheel directly, so the pulse rate to the PCM is ~x4 higher ! The Black Oak PCM is coded to take account, but causes confusion with a 'normal' gearbox. If you have other OBD signals on the Focus cluster then the speed should work ...... "

This got me hopeful but what then is the problem? I have a fairly sensible speed reading via OBD on my Android/Torque/Bluetooth OBD device but not on the dash.

I am left with the idea of a fault with either the ECU or two Speedos. I have just replaced the ECU and that didn't help either - so that's two ECUs and two Speedos! Seems quite unlikely that two items of the same sort should both be faulty...

I think I'll get another speedo as they're quite cheap on ebay, just in case - but I am beginning to think it is a wiring fault after all...

Just to re-emphasise - I do have a speed reading via OBD and also a nice speed related square wave pulse coming out of Pin 4 on the ECU (60pin version) that's used to control audio volume among other things. So if speed sensing on the dash is not by OBD data link then where should it be connected???