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Home >> Chevrolet >> 2012 >> Cruze Eco, Automatic Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 139 (Engine Controls And Fuel - 2.2L - DTC P0351 To DTC P2544) >> DTC P0412 or P0418 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2010 Pontiac G5 and 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, remove the appropriate relay.
  2. Ignition ON, verify that a test lamp illuminates between the relay coil B+ circuit terminal 86 and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.
  3. Verify a test lamp does not illuminate between the relay control circuit terminal 85 and B+.
    • If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
  4. Test for less than 1 V between the relay coil control circuit terminal 85 and ground.
    • If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Connect a DMM set to the diode setting between the control circuit terminal 85 and ground.
  6. Command the appropriate relay ON and OFF with a scan tool. The DMM should transition from 2.5-3.5 V when commanded OFF to less than 1 V when commanded ON.
    • If the circuit voltage does not correspond to the specified values, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  7. If all circuits test normal, test or replace the appropriate relay.
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