Description: Silverado, sierra. 5.3l. Upper. Left. 4.3, 5.3, 6.2L, 5.3, 6.2L. Silverado, sierra. 6.2l. Silverado, sierra. 4.3l. 4.3, 5.3, 6.2L, 4.3L. This part requires programming and/or special setup procedures GM Service Information describes the procedures and special tools needed to ensure proper operation in the vehicle Detects oxygen content in the exhaust gases to help optimize emissions This GM Genuine Part is designed, engineered, and tested to rigorous standards and is backed by General Motors