Scrapyard Challenge is a side mission located in the Autoyard, Harwood and can be activated by getting on the Sanchez near the car crusher. It is in GTA Liberty City Stories.
Once the player gets on the Sanchez you have to drive into coloured checkpoints which are red, amber and green. The checkpoints are worth points. Green = 1 Amber = 2 and Red = 3. If you get more than 22 points you pass the mission. The reward is 4x the money for vehicles crushed at the car crusher if you collect more than 22 points and 31 points will make the car crusher give you 8x the amount of money after you crush the vehicles. You need to complete this to get closer to 100%.