This is the stock TDI fuel temp sensor for all 1996-2003 U.S. Spec TDI engines. Also known as the G81, this sensor has a direct effect on start of injection. A bad sensor can make your timing unstable. Replacement of this sensor requires the Metalnerd MN3001 triangular socket which is available above for $23.00. You will also need a top quantity adjuster seal which is contained in the $21.00 Bosch Seal Kit above.