EL-39200-B Digital Multimeter (DMM)

CH-51450–LEAD-A Oscilloscope Basic Lead Kit

CH-51450–A Oscilloscope Diagnostic Kit

CH-51450-PROBE Pierce Probe Kit

For equivalent regional tools, refer to Special Tools.

Perform the following procedures while wiggling the harness from side to side. Continue this at convenient points (about 6 inches apart) while watching the test equipment.

• Testing for Short to Ground
• Testing for Continuity
• Testing for a Short to Voltage

If the fault is not identified, perform the procedure below using the MIN MAX feature on the EL-39200-B DMM. This feature allows you to manipulate the circuit without having to watch the DMM . The DMM will generate an audible tone when a change is detected.

1. Connect the DMM to both sides of a suspected connector (still connected), or from one end of a suspected circuit to the other. Refer to Troubleshooting with a Digital Multimeter for information on connecting the DMM to the circuit.
2. Set the rotary dial of the DMM to the V (AC) or V (DC) position.
3. Press the range button of the DMM in order to select the desired voltage range.

Note: The 100 ms RECORD mode is the length of time an input must stay at a new value in order to record the full change.

4. Select the MIN MAX function of the DMM. The DMM displays the 100 ms RECORD and emits an audible tone (beep).
5. Simulate the condition that is potentially causing the intermittent connection, either by wiggling the connections or the wiring, test driving, or performing other operations. Refer to Inducing Intermittent Fault Conditions.
6. Listen for the audible Min Max Alert which indicates that a new minimum or maximum value has been recorded.
7. Press the MIN MAX button until the MAX value is displayed and note the value.
8. Press the MIN MAX button until the MIN value is displayed and note the value.
9. Determine the difference between the MIN and MAX values.
• If the variation between the recorded MIN and MAX voltage values is 1 V or greater an intermittent open or high resistance condition exists. Repair the condition as necessary.
• If the variation between the recorded MIN and MAX voltage values is less than 1 V an intermittent open or high resistance condition does not exist.

Note: Front probing cannot be used for this test.

1. Probe the circuit at each end using approved probing procedures.

Refer to: Probing Electrical Circuits.

2. Connect the blue oscilloscope test lead to a probe on one end of the circuit and then connect the red oscilloscope test lead to the other probe on the other end of the circuit. Connect each test lead’s black cable to ground.
3. Connect both the blue and red test leads to channels A and B of the picoscope.
4. Connect the oscilloscope to the laptop using the blue USB cable provided in the pico kit. 
5. Launch PicoScope 7 for GM software.
6. Set channel A and B input range to the 20v scale.
7. Select more and then select ConnectDetect and ensure the display is green. If it is not green fix any probe connection issues and retry.
8. Select Scope and set Timebase to 50 ms/div.

Note: The following step adds a calculated channel onto the screen that will automatically subtract the voltage reading from channel A and channel B and display a third waveform accordingly.

9. Select ‘More ’and then select math channels. Click the checkbox for A–B.
10. Ensure scope is "Running" in the top left-hand corner of the screen.
11. Simulate the condition that is potentially causing the intermittent connection, either by wiggling the connections or the wiring, test driving, or performing other operations. Refer to Inducing Intermittent Fault Conditions.
12. Once the fault is duplicated, stop the scope capture by either hitting the space bar once or clicking the box that states ‘running.’
13. Review the waveforms for discrepancies.

Note: If the Math Channel shows activity when fault was active, the failure is high resistance between the probe locations. If the Math Channel is flat during the fault and the other two channels do not change from normal, the fault does not exist between the two test points.

14. Locate and repair the fault. This may require moving probes or isolating circuits.