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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 212 (Hybrid Engine Electrical System) >> Diagnostic Information & Procedures >> Battery Electrical Drain/Parasitic Load Test >> Load Test

Load Test

WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Refer to Battery Disconnect Caution .
NOTE: Do not turn the parasitic draw test switch to the OFF position with the engine running. Damage will occur to the vehicle's electrical system.
NOTE: The test switch must be in the ON position when removing the fuses in order to maintain continuity in the electrical system. This avoids damaging the digital multimeter due to accidental overloading, such as a door being opened to change a fuse.
IMPORTANT: The switch knob on the J 38758  is marked ON and OFF. When the switch knob is in the ON position, the circuit is closed and electrical current will pass through the switch. When the switch knob is in the OFF position, the circuit is open and electrical current will not pass through the switch.
  1. Disconnect the battery negative cable from the 12V battery negative terminal. Refer to Battery Negative Cable Disconnection and Connection .
  2. Install the female end of the J 38758  to the 12V battery ground terminal.
  3. Turn the J 38758  knob to the OFF position.
  4. Install the battery negative cable to the male end of the J 38758  .
  5. Turn the J 38758  knob to the ON position.
  6. Start the engine and activate ALL of the accessories, including the radio and air conditioning.
  7. Turn the ignition switch to the OFF position and remove the ignition switch key.
  8. Disconnect the scan tool from the vehicle, if one is installed.
  9. Open and close the driver door, and wait 2 minutes.
  10. Connect a 10A fused jumper wire to the test switch tool terminals.
  11. Turn the J 38758  knob to the OFF position. The current now flows through the jumper wire.
  12. Wait 1 minute. If the fuse opens, install an inductive ammeter and go to step 22.
  13. Turn the J 38758  knob to the ON position.
  14. Remove the fused jumper wire.
  15. Set a digital multimeter to the 10A scale.
  16. Connect the digital multimeter to the test switch tool terminals.
  17. Turn the J 38758  knob to the OFF position. The current flows now through the digital multimeter.
  18. Wait 10 minutes. Check and record the current reading.
    1. When there is a current reading of 2A or less, turn the J 38758  knob to the ON position. The electrical current will now pass through the switch.
    2. Then switch the digital multimeter down to the 2A scale for a more accurate reading when the J 38758  knob is turned OFF.
  19. Turn the J 38758  knob to the OFF position.
  20. Using the MIN/MAX function of the digital multimeter, monitor the average current drain for 5 minutes. The average current drain should not exceed 35 mA.
  21. If excessive current drain is not found at this time and there are no other apparent causes, monitor the parasitic drain overnight or during the day using the MIN/MAX function of the digital multimeter. This will determine if something has been activated during that time frame.
    22. NOTE: The test switch must be in the ON position when removing the fuses in order to maintain continuity in the electrical system. This avoids damaging the digital multimeter due to accidental overloading, such as a door being opened to change a fuse.
    IMPORTANT: Removing fuses, relays, and connectors to determine the failure area may wake up modules. You must wait for these modules to go to sleep or use the sleep function on the scan tool.
  22. When the vehicle has an unacceptable amount of parasitic current drain, remove each fuse one at a time until the current drain falls to an acceptable level. This will indicate which circuit is causing the drain. Refer to Power Distribution Schematics to diagnose exactly which part of the suspect circuit is causing the parasitic drain. In some cases a non-fused circuit or component, such as a relay, is the cause of excessive parasitic current drain.
  23. Repeat the parasitic current drain test procedure after any repair has been completed to make sure that the parasitic current drain is at an acceptable level.
  24. When the cause of the excessive current drain has been located and repaired, remove the J 38758  .
  25. Connect the battery negative cable to the 12V battery negative terminal.
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