Volvo Repair: no spark, flash flash flash, example 121

Question
hi there i have a 90   740gl i am getting no spark at the coil.  is there a way to tell if i need a new coil or if it is a diffferent electrical problem.  thanks   luke  

Answer
you would need to fault trace the ignition system with a test light.I would start with checking for diagnostic trouble codes.below is how to do so.most common fault would be a bad engine speed sensor or a bad igntion power stage which is next to the air cleaner housing on the left inner fender.try wiggling the wire to this.the speed sensor is behind the cylinder head on top of the transmission.

in the engine bay on the drivers side near the strut tower there is a small black box with a wire attached to it.place the wire in the terminal marked 2.turn ignition key on (not started)press the small button for 1 second and the code will be displayed as a series of flashes.a red led displays the codes.the code will be three digits.small pause in between flashes for a single number long pause between flashes for the next number.example 121 will be flash.....flash..flash.....flash.repeat three times or until first code repeats itself.to erase the code after all codes have been checked hold the button for a good 5 seconds then release the light should light steady,then press for another 5seconds.this will erase the codes.  email me the codes and i will tell you what they are..socket 2is the fuel system 6 is ignition.