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HOMESERVICE MANUALSCHEVROLET2007SUBURBAN C1500, 5.3 0REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1085 (ENGINE CONTROLS AND FUEL - 4.3L - TROUBLESHOOTING & DIAGNOSIS)POWERTRAIN RELAY DIAGNOSISCIRCUIT/SYSTEM TESTING
2007 Chevrolet Suburban C1500, 5.3 0

Circuit/System Testing

2007 Chevrolet Suburban C1500, 5.3 0SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2008 GMC Sierra and 2008 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
    IMPORTANT: You must perform the Circuit/System Verification first.
  1. Ignition OFF, disconnect the powertrain relay.
  2. Ignition ON, verify that a test lamp illuminates between the powertrain relay coil B+, and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the battery positive cable to the underhood fuse block.
  3. Ignition OFF, verify that a test lamp does not illuminate between the powertrain relay coil B+ circuit and the control circuit.
    • If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
  4. Remove the test lamp.
  5. Command the powertrain relay ON, with a scan tool. Verify with a scan tool that the powertrain relay Ckt. Short Volts Test Status parameter is OK.
    • If not the specified value, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  6. Test the coil side of the powertrain relay for 65-110 ohms.
    • If not within the specified value, replace the relay.
  7. Ignition OFF, disconnect the ECM C1 connector.
  8. Test the powertrain relay control circuit for an open/high resistance.
    • If the circuit tests normal, replace the ECM.
  9. Verify that a test lamp does not illuminate between the relay ignition 1 voltage circuit and ground.
    • If the test lamp illuminates, test the relay ignition 1 voltage circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  10. Verify that a test lamp illuminates between the relay switch B+ and ground.
    • If the test lamp does not illuminate, test the relay switch B+ circuit for a short to ground, or an open/high resistance. If the circuits test normal, and the fuse for the ignition 1 voltage circuit is open, test the ignition 1 voltage circuit to the ECM for a short to ground. If the circuit tests normal, replace the ECM.
  11. Connect a 20 A fused jumper wire between the relay switch B+ and the relay ignition 1 voltage circuit.
  12. Ignition ON, engine OFF, monitor the EC Ignition Relay Feedback parameter with a scan tool. The parameter should display B+.
    • If the parameter does not display B+, test the ignition 1 voltage circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  13. If all circuits test normal, replace the relay.
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