Speedo Stopped Work And Engine Idle Not Not Working Correctly

[Vitesse]

Anyone know the answer to this problem?

This is a Surf 3 litre TD manual 1994.

The other day the speedo stopped working and the engine idle is now a bit wrong. The idle is ok when braking from low speeds, but when coming from higher speeds...motorway, the engine nearly dies instead of going to the correctly idle speed when braking. I have replaced the speed sensor in the gearbox... no change. I have taken the kmh to mph converter from the back of the speedo of as well... no change...is it the ECU?

Thanks

[tilla531]

TPS sensor?

[Vitesse]

TPS sensor?

No it's not the TPS. When I disconnect the TPS the engine idles higher and the ECU reports a problem (Code 41). When I disconnect the speedo sensor the ECU reports no problems... strange since I've disconnected it. I would have thought it should give me a Code 42 error..... Anyone any ideas... next I'm going to try and see if the signal from the speedo sensor is getting to the speedo. The power is getting to the speedo sensor...it may not work, but it has power! It's strange that what ever is wrong it is effecting the engine and speedo.