The rear wiper is not listed in aftermarket application catalogs. This usually means you have to get a Toyota replacement at the dealer and they'll be able to look up size and the correct part number.
Front wiper options are available aftermarket - see related link.
The Toyota Echo has the most common hook-end wiper arms. See sources and related links below for installation videos. Also, purchase the replacement blades first and there will be additional instructions/illustrations on the replacement packages. Locate and press the tab or button where the wiper blade is inserted into the hook of the wiper arm and pull wiper blade out of hook. You may have to rotate and flex the blade to make enough clearance for the hook to pass through.
The 2003 Toyota Echo takes 22" drivers side and 14" passenger side replacement windshield wiper blades.
http://letmegooglethatforyou.com/?q=how+to+remove+wiper+arms
The 2001 Toyota Echo wiper blade sizes are 22" drivers and 14" passenger side wiper blades. Do not buy by length-only however. See Sources and Related Links below for more information. Since there are over 22 different wiper arm attachments - be sure to lookup exact wiper blade part numbers by vehicle make, model and year for the brand wiper you decide to purchase. This ensures correct length AND correct attachment.
The 2003 Toyota Echo (yaris) takes 22" drivers and 14" passenger side wiper blades. See sources and related links below for more information. Since there are over 22 different wiper arm attachments, do not buy wipers just by length only. Be sure to lookup exact wiper blade part numbers by vehicle make, model and year for the brand wiper you decide to purchase. This ensures correct length AND correct attachment.
http://pdftown.com/2000-2002-Toyota-Echo-Service-Manual.html
According to my reference, there was no 2004 Toyota Yaris but there is a 2004 Toyota Echo. (The Yaris replaced the Echo in 2006). See sources and related links below.
The 2002 Toyota Echo OBD 2 port is under driver side dash next to kick panel
It will depend on the brand and style of wiper you decide to purchase. It usually comes up as 13 or 14 but 14 is a hard size to find but gives you that little bit of extra coverage. Below are some options.
For my 2002 Echo it is 3.7 Liters with a filter change.
3.6 liters
To flush the coolant in a 2002 Toyota Echo you will need to drain it first. Flush with fresh water and then refill with coolant and distilled water.