Section 2 Automotive Maintenance and Repair,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments 7.2 Operation of OTC Enhanced Monitor scan tool Chapter 8 Reading Repair Manuel 8.1 Diagnosing Automatic Transaxle（A541E） 8.2 How to Read and Use Wiring Diagrams 8.3 How to Read Technical Service Bulletin,Chapter 7 Common Special Service Tools and Equipments,7.1 Functions of Diagnostic Equipments 7.2 Operation of OTC Enhanced Monitor scan tool,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,New Words,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,New Words,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,New Words,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,New Words,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,New Words,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,7.1.1 Non-Powered Test Lights purpose Non-powered test lights (Figure 71) continue to have a place in your toolbox for certain quick checks. However, many technicians continue to use these devices in circuits where they can be very dangerous; therefore, it is important to understand a few facts about them. The test lights only purpose is to serve as a quick-check tool to show if a voltage is present. Functional Procedure Begin by connecting the test light across the batterys terminals to verify the integrity of the test light. Then, while it is grounded, touch the circuit in question and note the light. A test light makes a great tool for testing all of the vehicles fuses in a short amount of time. It can also be used to test switching of circuits such as ignition coils and fuel injectors as long as the resistance of the test light equals or exceeds the resistance of the intended load.,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,A grounded test light can also be used to provide a path of low resistance for identifying poor insulation in secondary ignition wiring. Secondary ignition wiring that is arcing to ground can be difficult to identify in the shop when cylinder pressures are low and resistance across the plug gap is also low. But many times, even with the engine idling, a secondary wire will arc to a grounded test light to help identify the specific insulation breakdown. For this test, pass the tip of the grounded test light along each of the secondary wires with the engine running. 7.1.2 Digital Volt-Ohmmeters（DVOM） Purpose A DVOM is used by most technicians to make pinpoint tests of the computer and its associated circuits and components. A typical automatic-scaling DVOM is shown in Figure 72. A DVOM is generally the tool of choice for making accurate pinpoint tests of the electrical characteristics of a circuit.,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,Figure 71 A typical non-powered test light,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,Figure 72 A typical automatic-scaling DVOM,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,Functional Procedure Connect the black lead to the jack marked “Common” and the red lead to the jack marked for the type of measurement needed. Bear in mind that leads connected into the amp jacks effectively turn the DVOM into a jumper wire. Now set the dial to the scale needed. Connect the red and black leads to the circuit or component that you need to test, according to the type of measurement being made (voltage, voltage drop, amperage, or resistance). The red lead should connect to the point that is most positive in the circuit and the black lead to the point that is most negative.,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,Testing Available Voltage with a DVOM ：This testing is shown in Figure 73. Voltage-Drop Testing with a DVOM: To perform a voltage-drop test of a circuit, the DVOM must be connected in parallel to the circuitry. This parallel connection compares the difference between the two voltage values and displays the results (Figure 74). This difference is the amount of voltage drop that has occurred between the two points where the DVOMs leads are connected.,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,Figure 73 Available voltage test,Figure 74 Positive-side voltage-drop test. A 0.042-V reading indicates that insulated circuit resistance is acceptable.,Chapter 7 Common Special Service Tools and Equipments 7.1 Functions of Diagnostic Equipments,Using Voltage-Drop Tests to Identify Intermittent Problems within the Circuitry:It should be noted that voltage-drop test