Testing for Short to Ground

Danger: This procedure should not be performed on high voltage circuits. Performing this procedure on high voltage circuits may result in serious injury or death.

Caution: Refer to Test Probe Caution.

The following procedures test for a short to ground in a circuit.

With a Digital Multimeter (DMM)

  1. Fully isolate the circuit by disconnecting all connection points on the circuit. Depending on how the circuit is configured, this may include:
    • Fuses or fuse blocks
    • Relays
    • Control module electrical connectors
    • Component electrical connectors
  2. Set the rotary dial of the DMM to the Ω position.
  3. Connect one lead of the DMM to one end of the circuit to be tested.
  4. Connect the other lead of the DMM to a good ground.
  5. If the DMM does NOT display infinite resistance (OL), there is a short to ground in the circuit.

With a Test Lamp

  1. Fully isolate the circuit by disconnecting all connection points on the circuit. Depending on how the circuit is configured, this may include:
    • Fuses or fuse blocks
    • Relays
    • Control module electrical connectors
    • Component electrical connectors
  2. Connect one lead of the test lamp to battery positive voltage.
  3. Connect the other lead of the test lamp to one end of the circuit to be tested.
  4. If the test lamp illuminates, there is a short to ground in the circuit.

Fuse Powering Several Loads

  1. Review the system schematic and locate the fuse that is open.
  2. Open the first connector or switch leading from the fuse to each load.
  3. 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.
  4. Close each connector or switch until the DMM displays voltage in order to find which circuit is shorted.