Ive have a Volvo 740 1989 mod.
Engine: B230F

I'vo got the code 3-1-1 in my diagnosticbox.
And i have noticed some problem with my car, to get rpm sometimes.

So what is my problem?
where is it?
how do i fix it?
some pictures would make it alooot easier

thanks for any help

 

Genearally, the speedometer signal will be missing because of the sensor having failed or connections there are no good. It is located on the rear of your differential.

If it is good, then either the speedometer has become disconnected on the back side or the speedometer has failed.
Here's a picture of the speedometer...

And, because pictures always help...