GM Service Manual Online
For 1990-2009 cars only
    • J 38758 Parasitic Load Test Switch Tool
    • J 39200 Digital Multimeter
  1. Disconnect the negative battery cable. Refer to

    Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

    in General Information.
  2. Notice: The parasitic draw test switch should never be turned to the OFF position with the engine running. Damage could occur to the attached ammeter or the vehicle electrical system.


    Object Number: 143221  Size: SH
  3. Connect the J 38758 male end to the negative battery terminal.
  4. Turn the test switch knob to the OFF position.
  5. Connect the negative battery cable to the J 38758 female end.
  6. Turn the J 39200 to ON.
  7. Road test the vehicle with all of the accessories on.
  8. After the road test, with the ignition still in the ON position, shut down all power accessories including the Electronic Climate Control head.
  9. Turn the ignition to LOCK.
  10. Remove the ignition key.
  11. Set the ammeter to 10 A.
  12. Connect the J 38758 to the test meter terminals with alligator clips.
  13. Turn the J 39200 to OFF.
  14. Allow the current reading to stabilize for 20 minutes.
  15. • A reading below 25 mA is acceptable.
    • If the current reading is at or below 2 A, perform the following steps:
         1. Turn the J 39200 to ON.
         2. Switch the ammeter to a lower scale.
         3. If necessary, use a more accurate meter.

            Important: Always turn the test switch tool knob to the ON position before removing each fuse to maintain continuity in the electrical system and to avoid damaging the ammeter due to an accidental overload (i.e. opening door to change a fuse, etc.).

         4. Turn the J 39200 to OFF. If the reading is above 25 mA, begin removing fuses one at a time until the readings fall within specifications. When the fuse has been identified, refer to Diagnostic Information in Engine Electrical for detailed circuit information.
         5. A total reading below 20 mA is normal, and a reading between 20-25 mA is acceptable.
    • A zero reading indicates a problem with the meter, the scale being used, or a connection.
    • A reading above 100 mA may suggest the following:
       - Grounded wires
       - Sticking relays
       - A light is ON.
  16. When the cause of the current draw has been located and repaired, perform the following:
  17. 14.1. Repeat steps 11 and 12 above in order to verify the repair.
    14.2. Turn the J 39200 to OFF.
    14.3. Remove the J 38758 .
    14.4. Connect the negative battery cable.

    Tighten
    Tighten the negative battery cable to 6 N·m (53 lb ft).

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  18. After repairs have been made, recalibrate applicable accessories.