Diagnostic Aids

Code P0502 will set if no vehicle speed is detected at start off. Code P0503 will set when vehicle speed has been detected and lost. Inspect all harnesses and related wiring, including control module connectors.

Fig 1: Codes P0502/P0503 Schematic ("S" & "T" Series 4.3L - VIN W) VSS Circuit Low/High

Fig 2: Codes P0502/P0503 Flow Chart ("S" & "T" Series 4.3L - VIN W) VSS Circuit Low/High