Envoy, Rainer, Trailblazer 2006-2007

Testing For Electrical Intermittents

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Good Circuit Continuity



  1. Using a Digital Multi-Meter (DMM), test for circuit continuity by performing the following:
    1. Set the rotary dial of the DMM to the ohm position.
    2.  
    3. Disconnect the power feed (i.e. fuse, control module) from the suspect circuit.
    4.  
    5. Disconnect the load.
    6.  
    7. Press the MIN MAX button on the DMM.
    8.  
    9. Connect one lead of the DMM to one end of the circuit to be tested.
    10.  
    11. Connect the other lead of the DMM to the other end of the circuit.
    12.  
    13. If the DMM displays low or no resistance, the circuit has good continuity.
    14.  

  2.  
  3. Using a Test Lamp, test for circuit continuity by performing the following:
    NOTE
    Only use the test lamp procedure on low impedance power and ground circuits.

    1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.
    2.  
    3. Disconnect the load.
    4.  
    5. Connect one lead of the test lamp to one end of the circuit to be tested.
    6.  
    7. Connect the other lead of the test lamp to battery positive voltage.
    8.  
    9. Connect the other end of the circuit to ground.
    10.  
    11. If the test lamp illuminates (full intensity), then the circuit has good continuity.
    12.  

  4.  

Measure For Voltage In A Circuit



  1. Disconnect the electrical harness connector for the circuit being tested, if necessary.
  2.  
  3. Enable the circuit and/or system being tested. Use the following methods:
    1. Turn ON the ignition, with the engine OFF.
    2.  
    3. Turn ON the engine.
    4.  
    5. Turn ON the circuit and/or system with a scan tool in Output Controls.
    6.  
    7. Turn ON the switch for the circuit and/or system being tested.
    8.  

  4.  
  5. Select the V (AC) or V (DC) position on the Digital Multi-Meter (DMM).
  6.  
  7. Connect the positive lead of the DMM to the point of the circuit to be tested.
  8.  
  9. Connect the negative lead of the DMM to a good ground.
  10.  
  11. The DMM displays the voltage measured at that point.
  12.  

Short-To-Ground



  1. Using a Digital Multi-Meter (DMM), test for a short-to-ground by performing the following:
    1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.
    2.  
    3. Disconnect the load.
    4.  
    5. Set the rotary dial of the DMM to the ohm position.
    6.  
    7. Connect one lead of the DMM to one end of the circuit to be tested.
    8.  
    9. Connect the other lead of the DMM to a good ground.
    10.  
    11. If the DMM does NOT display infinite resistance (OL), there is a short to ground in the circuit.
    12.  

  2.  
  3. Using a Test Lamp, test for a short-to-ground by performing the following:
    1. Remove the power feed (i.e. fuse, control module) from the suspect circuit.
    2.  
    3. Disconnect the load.
    4.  
    5. Connect one lead of the test lamp to battery positive voltage.
    6.  
    7. Connect the other lead of the test lamp to one end of the circuit to be tested.
    8.  
    9. If the test lamp illuminates, there is a short to ground in the circuit.
    10.  

  4.  
  5. For checking the circuit at the fuse, perform the following:
    1. Review the system schematic and locate the fuse that is open.
    2.  
    3. Open the first connector or switch leading from the fuse to each load.
    4.  
    5. Connect a DMM across the fuse terminals (be sure that the fuse is powered).

      When the DMM displays voltage the short is in the wiring leading to the first connector or switch.
       
      If the DMM does not display voltage refer to the next step.
       

    6.  
    7. Close each connector or switch until the DMM displays voltage in order to find which circuit is shorted.
    8.  

  6.  

 
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