One problem related to check engine light on has been reported for the 1999 Toyota Prerunner. The most recently reported issues are listed below.
A rod was thrown through the engine block. The dealer claimed it was a maintenance problem where they refused any responsibility. 80,000 miles on the odometer. Purchased new engine and $8,000 had a new engine with a permanent check engine light illuminated. Dealer claims check light was a new problem and offered to fix for somewhere north of $1,500. Refused this fix. Oil was changed at regular intervals. Boo Toyota.