Lately, we’ve been discussing car starting problems and battery and charging system maintenance. But when it comes to car trouble, how do you pinpoint the source of the problem? How do you know if your maintenance plan is effective? You need a car diagnostic tool, like a digital multimeter (DMM) or an OBD2 scanner. When used with the car repair manual, DMMs and OBD2 scanners give you more in-depth information on how your vehicle is functioning and can help you diagnose faults and confirm your repairs. Read on to learn how to choose the best car diagnostic tools!
Choosing an OBD2 scanner
Choosing the right OBD2 scanner can be a challenge, but the task becomes easier once you’ve determined your specific needs. There are several levels and types of scanners, and their prices and capabilities vary across the board. Keep in mind that a professional OBD2 scanner can be used for more than just reading diagnostic trouble codes (DTC). Here are a few things to keep in mind when choosing a scan tool:
- Connections – An OBD2 scanner may be standalone or require a cable adapter or Bluetooth adapter. Standalone code readers and scanners don’t require any additional equipment. Just plug them in and they light up. To use your tablet or laptop as an OBD2 scanner, install the necessary software and use a cable adapter to connect your device to your car, or connect wirelessly using a Bluetooth adapter.
- Capabilities – The most basic scanners only read DTCs. You might have to look up the code online or in your repair manual for diagnostic steps. Advanced scanners and adapters feature a code description database, can clear codes, and show vehicle data, like engine speed or oxygen sensor voltage. Professional scanners feature more capabilities, like freeze-frame data, graphing drive data, and more.
Choosing a digital multimeter
Multimeters range from basic analog to digital and engineering grade. Basic multimeters generally measure voltage and resistance, and sometimes current. Others measure temperature, capacitance, duty cycle, and frequency, and may test diodes and transistors. For modern computer-controlled cars, analog multimeters are not recommended because they can overload certain circuits. In contrast, high impedance DMMs are safer for modern automotive circuits. Clamp multimeters measure current without interrupting the circuit. Auto-ranging DMMs, like this TrueBlue 31 Auto-Ranging Digital Multimeter, take the guesswork out of making and interpreting measurements. Choose a DMM with the following capabilities according to your needs:
- DC voltage – Measures the direct current (DC) voltage drop in live circuits, the battery open circuit voltage, or the available voltage at components.
- DC amperage – Measures the DC in live circuits, such as the alternator output, fuel pump draw, or parasitic draw.
- AC voltage – Measures certain automotive alternating current (AC) output signals, such as from wheel speed sensors and crankshaft position sensors.
- Resistance – Measures circuit resistance in disconnected components or unpowered lines.
- Continuity – Sounds an alarm when circuit resistance is close to zero ohms (Ω), which is useful when checking for short circuits.
- Temperature – Especially useful for checking the temperature of very hot elements, such as the engine cooling system thermostat.
Of course, even the best car diagnostic tools are useless without the knowledge and experience to interpret the results. Always check your measurements against the repair manual and speak with an expert for the best chance of a successful diagnosis and repair.
By Benjamin Jerew