Ive have a Volvo 740 1989 mod.
Engine: B230F

My rpm sensor is broken, said my diagnostic box.
So what is a RPM sensor??
Where is it??

Would be perfect if i could get a picture that shows where it is.

Thanks for any help

 

Rpm signal missing is more accurate. The rpm sensor, also called a crank sensor, crank angle sensor or CSS counts the revolutions of the crankshaft to inform the fuel computer what the engines revolutions are. It is mounted on the rear most portion of the engine block, right where it joins the bellhousing of the transmission. In the car, it is necessary to peer down between the cylinder head and firewall. On 740 motors, the cam mounted distributor makes it a bit tougher to see. The sensor is vital to the engine. With no signal, the engine will not run...period.
Here it is in the circled portion in the photo. Engine is out of the car of course.

Often times it is the pig tail connector or wiring that has failed. Note how long the connecting wire is...

Although the CSS mounts to the rear portion of the block, it extends back into the bellhousing of the transmission.