I have a 2001 4Runner SR5 and I regularly get beween 18 and 20 MPG I have a 1999 4Runner Limited and I too get around 19 mpg. I have a 1997 4Runner SR5 V6 4WD, 22MPG in summer for mixed driving, 24MPG in summer all highway at constant 78MPH. 18 - 20 MPG in winter mixed driving.
Remove the right front wheel and splash guard (rubber curtain) the starter will be right in front of you. You can not remove it from the bottom of the truck, it will not fit out that way. From the wheel well you will still need to manuever it around a bit, but that is how it comes out.
On a toyota tacoma 2003 SR5 when the tail lights are turned on the brake lights come on and when the tail lights are of the brake lights work just fine what could be the problem. If the truck has a trailer plug, inspect the plug and plug wiring for damage and corrosion.
start by removing the glovebox, that will expose the heater assembly. just above where your feet go, still on the passenger side, the motor is mounted with 3 torx type screws. unplug the 2 wire plug, remove the screws, and it should fall out in your hands!
My turn out to be a air/fuel ration sensor, the problem gave me a check engine light and also a "vsc trac off" and a "vsc trac" light making me think I had a bigger problem. Putting a new sensor in took care of all the lights. 2001 4Runner SR5 4wd.