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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 135 (12 V Starting And Charging - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> Battery Electrical Drain/Parasitic Load Test >> Circuit/System Testing

Circuit/System Testing

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NOTE:

Do not test for a voltage drop at the Junction Block Studs without wiring or cables attached to it. It will result in the DVOM providing a false reading.

GM5654572Courtesy of GENERAL MOTORS COMPANY
    NOTE:

    The Leg of the Battery Junction Block with the highest draw or voltage drop is likely to be the source of the excessive parasitic draw.

  1. If the equipped with a battery Junction block and if it is accessible, utilize and inductive amp clamp or perform a voltage drop test between the battery positive post and each leg of the battery junction block to help determine which fuse block is containing the draw.
    • If a Parasitic Draw has not been isolated in Step 1.
    • GM5646333Courtesy of GENERAL MOTORS COMPANY

      Standard Fuse Voltage Drop Test Example

    • GM5653612Courtesy of GENERAL MOTORS COMPANY
      GM5653617Courtesy of GENERAL MOTORS COMPANY
      NOTE:

      The center of the fuse is the supply voltage for both sides of the fuse.

      Micro 3 Fuse Voltage Drop Test Example

      NOTE:

      Some fuses that may have an initial voltage drop then drop off, and some fuses that always have a nominal draw going to components that supply memory retention is normal.

    1. Use a DMM set to mV scale and perform a voltage drop across each fuse excluding J-Case type fuses (ignore negative readings) one at a time to determine the fuse that is causing the parasitic draw using the tables and selecting the appropriate Fuse type. Refer to: Parasitic Draw Reference Table (Micro/Mini Fuses) , or Parasitic Draw Reference Table (Standard (ATO, ATC) Fuses) , or Parasitic Draw Reference Table (Maxi Fuses)
      • Go to next step: If a Parasitic Draw has been Isolated in Step 1
    2. Go to the fuse block that the draw has been isolated to.
      • GM5646333Courtesy of GENERAL MOTORS COMPANY

        Standard Fuse Voltage Drop Test Example

      • GM5653612Courtesy of GENERAL MOTORS COMPANY
        GM5653617Courtesy of GENERAL MOTORS COMPANY
        NOTE:

        The center of the fuse is the supply voltage for both sides of the fuse.

        Micro 3 Fuse Voltage Drop Test Example

      3. NOTE:

      Some fuses that may have an initial voltage drop then drop off, and some fuses that always have a nominal draw going to components that supply memory retention is normal.

    3. Use a DMM set to mV scale and perform a voltage drop across each fuse excluding J-Case type fuses (ignore negative readings) one at a time to determine the fuse that is causing the parasitic draw using the tables and selecting the appropriate Fuse type. Refer to: Parasitic Draw Reference Table (Micro/Mini Fuses) , or Parasitic Draw Reference Table (Standard (ATO, ATC) Fuses) , or Parasitic Draw Reference Table (Maxi Fuses)
    • If a voltage drop is found
      NOTE:

      Do NOT remove any fuses as it may cause the draw to go away and may not return. If the draw is isolated to a fuse that supplies voltage to more than one component, disconnect the components one at a time until the draw is gone.

      Refer to Power Distribution Wiring Schematics to diagnose exactly which circuit of the suspect system is causing the high parasitic drain.

    • Go to next step: If a voltage drop is not found
  2. Verify an excessive current draw is not present by removing each remaining J-Case fuse (s), circuit breaker (s), relay (s), components and modules one at a time while monitoring the draw to verify it drops to below 40 mA.
    • If an excessive parasitic draw is found
      NOTE:

      Do NOT remove any fuses as it may cause the draw to go away and may not return. If the draw is isolated to a fuse that supplies voltage to more than one component, disconnect the components one at a time until the draw is gone.

      Refer to Power Distribution Wiring Schematics to diagnose exactly which circuit of the suspect system is causing the high parasitic drain.

    • Go to next step: If an excessive parasitic draw is not found
  3. The condition may be an intermittent fault and is currently not present.
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