Troubleshooting with a Digital Multimeter |
Digital Multimeter (DMM) Basic Requirements |
1. |
Four digits displayed |
2. |
Voltage, amperage, resistance, frequency, diode test settings, and min-max function |
3. |
Display positive and negative values |
1. |
Have at least 10 MΩ input impedance |
2. |
Test a DC voltage range of 0.1-1000 V. |
3. |
Test an AC voltage range of 0.1-1000 V. |
1. |
Test a DC amperage range of 0.1µA-10 A. |
2. |
Test an AC amperage range of 0.1µA-10 A. |
1. |
Apply at least 1 mA when performing the diode bias test |
2. |
Display the break over voltage drop (0-3 V) of a forward biased diode |
3. |
Display infinite (O.L. (Over-load)) when a diode is reverse biased |
1. |
Can update at a 25 ms sample rate |
2. |
Saves and displays minimum and maximum values |
Note | ||
Circuits which include any solid state control modules, such as the engine control module (ECM), should only be tested with a 10 MΩ or higher impedance digital multimeter such as the EL-39200. |
Note | ||
Always disconnect the power to a suspect circuit when the resistance is measured using a DMM. Otherwise, the readings will be incorrect. A multimeter always measures resistance using a very low voltage. If another voltage is also present at the time, the reading can be incorrect. |
• |
Probe both ends of the connector and either hold the leads in place while manipulating the connector or tape the leads to the harness for continuous monitoring while you perform other operations or test driving. Refer to Probing Electrical Connectors. |
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Disconnect the harness at both ends of the suspected circuit where it connects either to a component or to other harnesses. |
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If the system that is being diagnosed has a specified pinout or breakout box, it may be used in order to simplify connecting the DMM to the circuit or for testing multiple circuits quickly. |