Comprehensive Components: Notes

Along with the major monitors, OBD II requires that the diagnostic system monitor any component that could affect emissions levels. In many cases, these components were being tested under OBD I. The OBD I requirements focused mainly on testing emissions-related components for electrical opens and shorts.

However, OBD II also requires that inputs from powertrain components to the PCM be tested for rationality  , and that outputs to powertrain components from the PCM be tested for functionality  . Methods for monitoring the various Comprehensive Component monitoring include:

1. Circuit Continuity
   • Open
   • Shorted high
   • Shorted to ground
2. Rationality or Proper Functioning
   • Inputs tested for rationality
   • Outputs tested for functionality
   NOTE:

   Comprehensive component monitors are continuous. Therefore, enabling conditions do not apply. All will set a DTC and illuminate the MIL in 1- trip.