Speedo under reading

[Jon TVR]

Took the tuscan out today and it rewarded me with a charaterful speedo needle.

It started to under read and now when I turn the engine off it rests on the bottom of the clocks I.e past the 0 mph Mark.

Also now got a b error code.

Anyone got any ideas?

[NorfolkSteve]

Mine does this for a past time.

I find that keying it on and off two or three times resets it. Don't know what the root cause is though as the digital speed reading is always OK.

Mine also will start to read ~20-25mph high, if speed exceeds somewhere in excess of 110+mph, again this will reset when ignition is turned off (best done when stationary!)

There have been many comments on here about faulty / dirty speed sensors, however I would have expected this to affect the digital reading as well.

[nrick]

It should reset every time that the ignition goes off/On.

Code B is the speedo not reseting back to its zero.

Might be the sensor, but the best thing to do is to make sure there is no obstruction, it isn't hitting the glass etc and reset it a few times.

If it doesn't go back to 0 then there is a problem, mine overreads sometimes if I am giving it some beans, wheelspin and hard acceleration seem to give it a hard time.

Could check the distance between the sensor and the ring, it isn't dirty or if possible swap out the sensor. If that fails then Cath might have a look at it for you.

HtH

N