Ignition coil is what will fire up a spark on the spark plug. Without it or if it malfunctions, that particular cylinder will not fire and you'll get a "miss", loss of power, etc. The 1999 S70 uses a COP or Coil On Plug design. Each spark plug has it's own coil. If one goes bad, the OBDII scanner should pick up a code directing you to the correct cylinder that has the bad coil.
No
Pull the plastic cover off the top (head) of your engine the coils are lined up on the top of your engine. Next you will need to unplug the coils from the connecting wires. After you unplug them you can simply pull the ignition coils out and replace them with your new ones.
"Ignition" is a system, of which the coils, spark plugs, wires and other components are a parts of. You need to be more specific with your question.
One per plug.
I am no mechanic but i just had my ignition coils changed on my ford expedition and there are 8 it was expensive to fix .
under the plastic cover on top of the engine, you will need a torx fitting to remove the cover, then the coils are on top and spark plugs below the coils, very easy to replace, coils are just 1 10mm bolt each
No, not if it is not defective. If the ignition switch is defective then that is all you need to replace.
You do not need a key to replace the ignition switch.
On a 2001 Volvo S40, ignition coil B is located on the engine's cylinder head, specifically for the second cylinder from the timing belt side. The ignition coils are arranged in a line, with each coil corresponding to a specific cylinder. To access it, you may need to remove the engine cover and possibly other components obstructing the ignition coil. Always refer to a repair manual for detailed guidance specific to your vehicle.
Here's a great video showing how to remove and replace the ignition coils. Your PCM will need to be repaired at the same time: http://www.youtube.com/watch?v=QWUduwyJYCY
depending on your mileage, you need to replace your sparkplugs, and ignition coils. you can get spark plugs from almost any auto parts store. I got 4 karalyn version R ignition coils from www.ecstuning.com for around $28.00 apiece and the tool to pull them out was $10.00
I would need a bit more information. Is is a 4 cylinder, or 6? I'm going to assume it's a 6. Do you see three ignition coils on top of the engine? Those coils are sitting on top of the ignition module. You will need a 7mm wrench to loosen the retaining screw for the module pigtail, and a 7/32 socket to remove the retaining screws for the coil. Once the coils are removed, you should find that the module comes off the mounting bracket with the final coil.