Code 68 SH reader

[ewan221]

Was having a play with my new fault code reader and only code is 68 - Road speed sensor output too ow at medium rpm and high air flow, which apparently points to a sensor or wiring fault.

Interesting as I got car the speedo packed in and the sensor was changed now the speedo works fine after 15-20 mph but nothing below these speeds.

Any idea where else I should look ?

[Ribol]

It might be worth checking the gap is set correctly for starters.

[ewan221]

Pretty sure the gaps ok

[Ribol]

ewan221 said:

Pretty sure the gaps ok

What is it set to?

[ewan221]

was set at 10 thou and it was not working under 25 mph, now moved as close as possible without the toothed wheel hitting it - now working over 15 mph

[Ribol]

When the speedo is working is it reading reasonably accurately?

[ewan221]

Have not really checked but appears to. Good point though will stick the sat nav in car next time I'm out

[scotty_d]

The gap is the thickness of an sheet of paper it is really that close like 1-2 thou. 10 thou is quite a lot for these annoying things lol

[Ribol]

scotty_d said:

The gap is the thickness of an sheet of paper it is really that close like 1-2 thou. 10 thou is quite a lot for these annoying things lol

The point is if everything was working as it should he would not have a problem at 10 thou, so something isn't right.

[ewan221]

It's ad close as you can get now, any closer the teeth would be hitting sensor. Checked Speedo accuracy this morning and that's all ok

[Ribol]

I would try and borrow a known working speedo from someone (mid dash swap?) and see if that fixes it

[blitzracing]

I think (?) there may be two outputs from the speedo calibration unit- one to the speedo for actual speed, and one for the ECU. What speed reading are you getting from the ECU mate? The TVR signal goes from 0 mph to some fixed speed (I dont know the value) at 0ver 3 mph that the ECU mate should report back. The error code is saying that the ECU thinks the car is moving,(lots or air and throttle) yet the speed sensor says otherwise.