Engine Diagnostic Tools

Car engines contain a lot of working parts, but diagnostic tools are designed to decipher problems.

Vehicle engines are a complex system of wires, moving parts and computerized controls. If an engine is not operational or is running poorly, engine diagnostic tools can help determine the cause of the problem. Such tools can be utilized to check many different engine systems, such as the electrical or computer-driven operations. Other tests can determine if the engine’s moving parts are in proper working order.


A voltmeter is equipped with two leads and can help diagnose electrical problems.

A voltmeter can take a measurement of the electrical currents flowing through various engine components and can be used to find faulty wiring. The device can also test ignition coils or relay switches to determine if those parts are preventing an engine from starting. Voltmeters are also helpful in testing the electrical charge in the vehicle’s battery. Although high-end models can cost considerably more, a basic voltmeter costs about $20.

Compression Tester

Automobile engines use air in the spark plug firing process, so testing the compression of the cylinders can give an indication of the motor’s health. Specifically, low compression can indicate a worn exhaust valve, a bad head gasket or other significant problem. A vehicle’s compression can be tested manually, which requires a gauge, or, on newer vehicles, electronically. If the compression is tested manually, each of the spark plugs must be removed and the ignition coils must be disabled.

OBD-ii System

Most late-model vehicles are equipped with an OBD-ii system, which stands for on-board diagnostics. This system can be plugged into a OBD reader that can then interpret data obtained by the car’s on-board computer system. The reader can often pinpoint malfunctioning engine components. There are three types of OBD-ii systems and those generally are made for the three different types of circuitry: those of European and Chrysler vehicles, those of General Motors vehicles and those of Ford vehicles. The OBD-ii system also captures the reasons that a vehicle’s check engine light goes on or off. A reputable mechanic will have access to an OBD-ii reader, or the device can be purchased for about $200.