See related link. It could be any number of things, you need to run some tests. Could be as simple as a blown fuse. Low pressure is probably most common. You may or may not have a leak that needs fixed (could be caused by a worn o-ring / gasket). Worst case you need a new compressor. You can buy a cheap gauge from harbor freight or take it to a professional.

The lighter fuse of a Toyota Matrix is located under the driver side dash of the vehicle. It is the 15 amp fuse in slot 1.

If it ain't broke, don't fix it. If it is broken, it depends on that you mean by "serviced". A replacement could be several hundred dollars, your best bet might be to find a good mechanic and call around, they should be able to give you an estimate. Find a mechanic here:
http://cartalk.com/
(Mechanic's Files - enter your zip code and read the reviews!) Additional: if you pay for a fuel injection cleaning you are getting ripped off. try a bottle of stp fuel injection cleaner and do it yourself. you'll save a lot of money and be doing exactly what the mechanic will do. if they are actually going to clean your fuel injectors it might be a different story, but be skeptical of "fuel injection services"

p0420 is the only common fault I know of for the Echo. The software is too sensitive, this could possibly be fixed with a firmware upgrade which is exactly what Toyota did for the Rav4 which had the same problem, but in the case of the Rav4 they issued a recall. The Echo has NOT had a recall for this issue. The car will often run fine, pass emissions tests, and get normal fuel economy even after the p0420 code comes up. The dealer will charge $1400 to put in a new catalytic converter (they replace the full assembly from engine to tailpipe). If you decide to save by using an aftermarket cat the p0420 code will in many cases will come right back. Of course the code can be caused by other things too like O2 sensors or MAF, but often replacing these will not be enough to keep this code from coming back.

Pop the hood, find the horn (small round thing) near the front grill toward the center. Use a multimeter to see if it is getting power. Check the fuse box, look for an open fuse. You can easily replace the horn.

yes

Needle nose pliars or a fuse puller?

Replacing (or tightening) the main drive belt is very easy, you will need a 12mm socket wrench and a 14mm open end wrench. Loosen (do not remove) the two bolts above the alternator that are attached to the metal bracket that allow the alternator to slide (the alternator is attached to the topmost pulley that the drive belt touches, it is at the top front passenger side of the engine compartment). There is a 3rd bolt below the alternator, slightly difficult to see, loosen it using the 14mm wrench, it is often difficult to turn, I recommend penetrating oil and a breaker bar, you only need to turn it a little bit to allow the alternator to pivot. Once all three bolts are loose, you can easily rock the alternator back and forth (same procedure is used to tighten the drive belt). You want to push the alternator back to remove the belt. After installing a new belt (or to tighten an existing belt) you need to pull the alternator toward the front of the car as far as possible. The best way to do this is by putting a pry bar on top of and slightly behind the alternator and pushing up toward the windshield while using the engine as a pivot - this gives you plenty of leverage and allows you to pull the alternator forward. While you are prying, you can tighten the bolt that holds the alternator to the bracket using your left hand as you brace the pry bar with your right hand, to hold it all in place.
The power steering belt is much more difficult but there is an adjustment bolt there as well (I recommend you don't replace that belt unless you have to).

Yes, see link, but note: I would just by a multimeter instead of a test light (you can get a multimeter for as little as $3 from harbor freight)

A defective vacuum line can cause a whistling sound when the vehicle is accelerating. A loose belt can also create a high pitched whistle sound.

You wait until it falls off on its own.

I have a 2000 echo and was faced with same thing. Cable would not open hood. I was able to detach the plastic grille from the front with very little damage to the plactic catches that hold it in place. Then snaked something up to the latched and popped it. Then I cut off the plastic coated cable with enough length to loop it out the front so that just a tug on the loop and the hood opens. Just like the old days when you opened the hood on all cars from outside. I like it better.

There are 2 lights , one blue, one red , they both will come on at starting , blue first then red , but that is to see if the are working , if you are driving normally and one of em comes on it means , Blue: Youre driving in very cold weather amd the coolant it getting below freezing point ,.( which is higly unlikely)

Or Red: your car is overheating

Can be a leak , defective water pump , thermostat , temp sensor

Akio Toyoda

Remove the glove box door by sqeezing the sides together and lift out. Remove the snap-in cover from the ECU area. Remove the 2 screws holding the ECU and disconnect the plugs, dont worry they only fit back in one way. Remove the 3 screws holding the fan motor in from below and it should come right out. Disconnect the wiring plugs and the entire blower/motor assembly will come out.

I'll leave the other comments below, but as a Toyota echo owner, I bet the sound you refer to is the sound of the fuel tank equalizing pressure, I own two echos and both do this, its a very odd "feature" of the echo, mine sound like croaking frogs, it can go on for quite a few minutes after you park the car. I assure you this is perfectly normal and there is nothing to fix. If this is the sound, you should be able to hear it much louder when you put your ear next to the fuel inlet.

The sucking sound is going to be already there but you can more than likely only here it for a couple of seconds after you turn the engine off.

This is more than likely going to be a vacuum hose or pump of some sort and usually depending on the type of vehicle you have I would take a guess and say the thing that you would usually expect this type of noise to be coming from the Brake Servo Vacuum Hose (Pressure Releasing from the unit) this maybe the result of having an air leak in one of the hoses and therefore creating this noise once you switch off the engine. In Normal circumstances you would not hear this because every hose and the unit itself is contained and sealed therefore releasing the pressure over a period of hours not seconds.

It certainly points towards an air leak of sorts even if you find it is not the Brake Servo. There maybe several other vacuum hoses located on the engine so it is just a process of elimination. I would definitely check the Brake Servo first though. just by placing your head next to the unit (either Bulk Head left or Bulk Head right) which is usually a black unit with the Master Cylinder (Where you put the Brake Fluid in) mounted on the front of it.

Hope this Helps