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Home >> Chevrolet >> 2009 >> TrailBlazer 4.2 S, 4WD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - 4.2L - DTC P0366 T0 DTC P2544 >> DTC P0685 or P0690 >> Circuit/System Verification

Circuit/System Verification

  1. Ignition ON, verify that the Feedback Circuit parameter indicates B+ voltage.
  2. Ignition ON, command the powertrain relay ON and OFF. Listen or feel to verify that the powertrain relay turns ON and OFF with the commanded states.
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