Volvo Repair: Check Engine light 96 Volvo 960, flash flash flash, example 121

Question
Hi
The other day the check engine light came on and stayed on. I checked all fluids and when I checked for engine codes with the small wire in terminal#2 and the key on the little red led was on solid. As I was checking the codes I heard a faint humming noise. I put my hand on the air cleaner box and felt a vibration. as I moved my hand up the main hose coming from the air cleaner box the vibrations increased. not being familiar with all the names of the parts I'm pretty sure I felt where the vibrations were coming from. It was closer to the opposite end of the air cleaner hose.
Is this normal
Did I check the engine codes properly.
What are some other reasons the light could be on.
Please help
Neal

Answer
sounds like the idle speed motor was making noise you may have entered the wrong mode an made the motor work.below is how to check for codes.there are many things that can make this light come on.check the codes first then go from there.




n the engine bay on the drivers side near the strut tower there  are 2 small black boxes one has  a wire attached to it.place the wire in the terminal marked 2 on the box marked A .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..