If the engine will not crank over, the most common problem is the starter. These will tend to go out at about 100,00-125,000 miles. Sometimes it is only the starter solenoid, but often the complete starter (including solenoid) needs to be replaced.
Problems for specific Toyota 4Runner years:
Car problem reports
Problem with your car? See what our experts say or submit your own.
Repairpal verified 2005 Toyota 4Runner problems
If the car will not start, the most likely problem is worn or corroded solenoid contacts in the starter. Usually, these parts can be replaced without purchasing a new starter.