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The Top 5 Engine Diagnostic Tools Every Mechanic Needs

Having the right tools in your garage can make all the difference when it comes to diagnosing and resolving issues with your vehicle’s engine. With onboard computers and complex systems in modern cars, you need more than just a basic set of wrenches and screwdrivers. Advanced diagnostic tools help pinpoint problems quickly and accurately.

In this guide, we’ll cover the top 5 engine diagnostic tools that every DIY mechanic should have. We’ll look at what they do, examples and prices, and when each tool is most useful. We’ll also go over factors to consider when selecting diagnostic equipment. By the end of this article, you’ll have a solid understanding of must-have diagnostic tools to troubleshoot your engine and keep your vehicle running smoothly.


Having a reliable vehicle is important, but engines can be complicated. When the dreaded check engine light illuminates, it could point to dozens of different issues, ranging from minor to major. Without the proper diagnostic tools, tracking down the exact cause can be like finding a needle in a haystack.

The good news is that advancements in diagnostic technology have made engine troubleshooting much easier for the average DIY mechanic. Gone are the days when you had to guess what was wrong based on basic measurements and visual inspections. Modern scanners and testers allow you to pinpoint problems quickly and accurately.

In this guide, we’ll explore the top 5 engine diagnostic tools that every DIYer should have in their toolkit:

  1. OBD2 Scanner
  2. Digital Multimeter
  3. Compression Tester
  4. Timing Light
  5. Borescope Camera

We’ll look at the key features and benefits of each tool, examples and pricing, when to use them, and any limitations. We’ll also go over factors to consider when selecting diagnostic tools for your needs and skill level. Let’s dive in!

Top 5 Engine Diagnostic Tools

1. OBD2 Scanner

An OBD2 scanner is the most basic diagnostic tool that every mechanic should own. OBD stands for On-Board Diagnostics generation 2, which refers to the standard diagnostics system built into all vehicles manufactured since 1996.

The main purpose of an OBD2 scanner is to retrieve trouble codes from the engine control unit (ECU) when the check engine light comes on. It connects to the diagnostic port usually found under the dash. Here are the key benefits of OBD2 scanners:

  • Read and clear generic and manufacturer-specific trouble codes
  • View “freeze frame” data taken when a code triggers
  • Check emissions readiness and test results
  • Access live data from sensors and modules
  • Perform basic actuations like turning off the check engine light

OBD2 scanners vary widely in price and capabilities. Simple code readers can be had for as little as $20, while advanced professional-grade scan tools run over $1000. Some popular mid-range options are:

  • Innova 3040c – $100, reads and clears codes, battery/alternator test
  • BlueDriver Bluetooth – $100, uses your smartphone, reads and clears codes
  • Autel AutoLink AL319 – $250, enhanced diagnostics beyond basic OBD2

The limitation of basic OBD2 scanners is that they only read generic codes common to all cars. For detailed manufacturer-specific codes and data, you’ll need an enhanced scanner. However, a code reader is the essential first step in diagnosing check engine lights and is useful for do-it-yourselfers.

2. Digital Multimeter

A digital multimeter (DMM) measures electrical values like voltage, current, and resistance. Having a DMM enables you to diagnose electrical issues and check if components are getting power and working properly. Key features include:

  • Measures voltage, current (amps), and resistance
  • Tests continuity to check for breaks in wiring
  • Measures duty cycle of signals
  • Features audible continuity tone
  • Displays minimum, maximum, and average readings
  • Auto-ranging to select measurement scale automatically

You can get a basic digital multimeter for around $50, or pay over $100 for one with more advanced capabilities from brands like Fluke or Klein. When choosing a DMM, look for:

  • Accuracy – the more accurate the better
  • Utility – get clamp probes, temperature sensor etc if needed
  • Reliable brand – Fluke, Klein Tools, Amprobe, Tekpower
  • Safety ratings – CAT III or CAT IV for automotive use
  • Warranty – 3 years or more on midrange DMMs

A digital multimeter is useful anytime you need to test an electrical circuit:

  • Diagnose bad fuses, relays, switches, sensors
  • Check battery charge and alternator output
  • Bench test components like starters and coils
  • Find wiring breaks or shorts
  • Confirm signals from modules to components

The main limitation is that a DMM only measures fixed circuits. For live data you’ll need a scope or scanner. But a DMM is cheaper and easier to use than a scope for basic tests.

3. Compression Tester

A compression tester is used to measure the compression pressure inside the cylinders. Compression issues can cause poor performance, hard starting, and misfires. Here’s how a compression tester works:

  • Gauge attaches to the spark plug hole
  • You disable ignition and crank the engine
  • The gauge shows compression readings for each cylinder

Look for a compression tester kit that includes:

  • Gauge with at least 160 psi capacity
  • Hoses and fittings
  • Adapters for different engine types
  • Instructions

Prices range from around $40 for basic testers to $200 for commercial grade kits with better gauges and accessories. Brands like OTC, INNOVA, and Craftsman make affordable testers suitable for home mechanics.

The main uses for a compression tester include:

  • Diagnose the cause of engine misfires
  • Test engine condition on older high-mileage vehicles
  • Check for major issues like burnt valves or blown head gaskets
  • Compare compression between cylinders to pinpoint weak ones

Compression testers have some limitations:

  • Only works on gasoline engines, not diesel
  • Requires disabling ignition system during test
  • Results can vary based on battery charge and starter speed

Still, a compression tester is a vital tool for assessing the internal condition of your engine.

4. Timing Light

A timing light is used to check ignition timing by visually inspecting the timing marks on the crankshaft and camshaft pulleys. Timing refers to the precise moment when the spark plug fires relative to piston position. Here’s how a timing light works:

  • Clamps inductively over the spark plug wire
  • Flashes a strobe in sync with the ignition pulses
  • Allowing you to view timing marks on the pulleys while running

Basic timing lights cost around $50. Look for a light with:

  • LED brightness to easily see the marks
  • A dial to adjust flash rate if needed
  • Alligator clamps for battery power
  • Solid build quality from brands like Innova

Proper ignition timing is crucial for engine performance and preventing damage. Symptoms of bad timing include:

  • Poor acceleration
  • Rough idle
  • Backfiring or misfiring under load
  • Engine knocking or pinging
  • Reduced fuel economy and power

Using a timing light allows you to check for:

  • Jumped timing from a slipped timing chain
  • Stretched timing chain or belt
  • Bad distributor advance mechanisms
  • Retarded cam timing

The main limitation of timing lights is that they only work on older distributor-based ignition systems, not modern computer-controlled engines. But they still have use for inspecting timing components.

5. Borescope Camera

A borescope is a flexible inspection camera that allows you to look inside the cylinders and down intake ports. Having a visual of the engine internals can reveal issues like:

  • Burnt, bent or broken valves
  • Cracks or holes in pistons
  • Scoring/grooves in cylinder walls
  • Blocked/collapsing lifters
  • Carbon buildup on valves and ports

A basic 1 meter borescope can be purchased for around $100. Look for one with:

  • At least a 5.5mm camera for fitting in spark plug holes
  • LED illumination
  • 640×480 resolution or better
  • Compatible with Android/iOS devices
  • Semi-rigid cable to maneuver inside passages

While borescopes take practice to use properly, they are invaluable for diagnosing internal engine issues without major disassembly. Limitations include:

  • Can’t see far down cylinders in some engines
  • Requires small openings to insert camera
  • Images can lack detail compared to physical inspections

Even with these limits, a borescope allows you to inspect areas impossible to see otherwise. The insights it provides are well worth the cost for any serious mechanic.

How to Choose the Right Diagnostic Tools

With the top 5 engine diagnostic tools covered, how do you determine which ones to get for your needs and skill level? Here are some tips:

  • Start with basics – An OBD2 scanner and multimeter are the core must-haves. Learn to use them effectively before investing in advanced tools.
  • Consider your mechanical skills – Tools like borescopes and advanced scanners require more knowledge to use properly. Build up your experience before jumping into complex diagnostics.
  • Determine must-have features – Don’t overbuy on features you may never need. But don’t sacrifice essential functions just to save money either.
  • Buy quality you can grow with – Purchase the best quality tools you can afford from reputable brands known for durability and accuracy.
  • Think long-term – How will your diagnostic needs change as you work on newer/more complex vehicles? Choose tools that will still be useful down the road.
  • Mix and match – You don’t have to buy an all-in-one kit. Create your own toolkit selecting individual tools that make sense for your projects.

The right diagnostic tools save a ton of guesswork and frustration when dealing with engine issues. Invest wisely and build your capabilities over time, and you’ll have the power to accurately pinpoint problems across many systems and vehicles.

Frequently Asked Questions on Engine Diagnostic Tools

What is the check engine light and how can an OBD2 scanner help?

The check engine light (CEL) illuminates when the vehicle’s OBD system detects an issue. An OBD2 scanner lets you retrieve diagnostic trouble codes that help identify the problem. Without scanning the codes, you don’t know what’s wrong when the CEL comes on.

Should I buy an inexpensive or expensive OBD2 scanner?

It depends on your needs. A basic inexpensive code reader is fine for DIY use to read and clear generic check engine codes. For advanced diagnostics, live data, and manufacturer-specific OEM codes, an expensive professional-grade scanner would be better.

What features make a digital multimeter useful for diagnostics?

Key DMM features include voltage, current, and resistance measurements, continuity testing, diode testing, signal measurement, and accuracy. These capabilities let you check electrical circuits critical for diagnosing problems.

When would I need a compression tester?

Check compression when an engine has a misfire, lacks power, burns oil, starts hard, or has high mileage. Compression testing can detect leaks, bad rings, burnt valves, and other internal mechanical issues.

Why is a timing light important?

A timing light lets you visually inspect cam/crank timing marks while the engine is running. This is necessary to check for timing chain slack, jumped timing, and issues with variable valve timing components.

How does a borescope camera allow you to see inside the engine?

A borescope uses a thin flexible cable with a camera on the end. It can be inserted through any small opening to look inside the engine. This allows you to visually inspect cylinders, valves, pistons, and other internal components.


Diagnosing modern engine issues requires having the right tools for the job. While a basic socket set is still essential, new problems require advanced diagnostic capabilities. With the technology built into vehicles today, it’s impossible to troubleshoot effectively without scanners and testers.

We’ve covered the 5 most important engine diagnostic tools that should be in every DIYer’s toolbox. Start with essentials like an OBD2 scanner and multimeter. Then add tools like compression testers, timing lights, and borescopes as your needs and skills grow. Diagnostic equipment is an investment, but it pays for itself many times over by empowering you to keep your vehicles running right.

Remember to build up your diagnostic knowledge alongside your toolkit. Learn how to use OBD2 scanners to their full potential. Practice testing components like alternators, starters, sensors, and circuits with a multimeter. Study up on compression and timing specifications. And get the knack of maneuvering a borescope camera inside tight spaces. Developing your skills will ensure you get the most out of any tool.

With this guide, you now have an overview of the top 5 picks for engine diagnostic equipment. The right tools combined with your mechanical know-how will have you tracking down and fixing issues like a pro. Drivers no longer have to simply guess at what could be wrong with their check engine light on. Arm yourself with the power to diagnose and resolve engine problems quickly and with confidence.



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