Comprehensive Components

Along with major monitors, OBD II requires that diagnostic system monitors 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 PCM be tested for rationality, and that outputs to powertrain components from PCM be tested for functionality. Methods for monitoring 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.