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  • Scan tools provide you with live data and are significantly more in-depth with their diagnoses than code readers.
  • Code readers are used to retrieve and clear DTCs, displaying generic codes to let you know if there’s anything wrong with your vehicle.
  • If you prefer to get your hands dirty and diagnose your vehicle yourself, you’re better off with a scan tool.
  • If you’d rather have diagnostics performed for you, a code reader is your best bet.

There’s a common misconception amongst DIYers (and even some professionals) that all scan tools and code readers are created equal. You might think that code reader you bought online for $9.95 is going to give you the same information as the dealer’s super-expensive scanner, but that’s not the case.

The truth is, there are a wide array of scan tools and code readers, all of which provide different levels of information and functionality.

Regardless of whether you’re shopping for new equipment or you’re just looking to expand your knowledge, it’s helpful to know what kinds of tools are available to help you troubleshoot your vehicle.

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There are a wide array of scan tools and code readers, all of which provide different levels of information and functionality.

What is Onboard Diagnostics (OBD)?

Before we dive into the different types of scan tools and code readers, it’s helpful to have a refresher on the basics of onboard diagnostics (OBD). In a modern OBD system, a computer (referred to as a control module) monitors various sensors and circuits, looking for problems. If the module detects an issue, it stores a corresponding diagnostic trouble code (DTC) in its memory. That DTC can then be retrieved using a scan tool or code reader to help troubleshoot the vehicle.

What’s the Difference Between a Scan Tool and Code Reader?

Contrary to popular belief, code readers and scan tools are not the same things. Scan tools are far more comprehensive than code readers.

Code Reader

A typical code reader can only handle two primary tasks: retrieving and clearing DTCs. Some code readers can also display readiness monitors and freeze-frame. Readiness monitors indicate the state of the onboard diagnostic system’s self-tests, whereas freeze-frame displays the data that was present if and when any DTCs were set.

Scan Tool

Meanwhile, a scan tool can display everything a code reader can, plus live data. Live data allows you to view select engine operating parameters in real-time. Some high-end scanners can also perform bi-directional tests and other advanced functions.

Generic vs. Manufacturer Specific Codes and Data

One often overlooked distinction is the difference between generic and manufacturer-specific diagnostic information. Most code readers can only display generic information (and sometimes manufacturer-specific powertrain codes, but without definitions), while some higher-end scanners can display both types of information.

Generic OBD2 Codes and Data

All vehicles model year 1996 and newer support a selection of generic OBD codes and data known as global OBD2. The information is considered generic or “global” because it’s defined by the Society of Automotive Engineers (SAE) rather than the vehicle manufacturer.

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An example of a generic OBD2 engine data list retrieved from a 2008 Ford Escape Hybrid.

An individual vehicle will only support a portion of the available generic OBD2 codes and data. Exactly what information is supported will depend on the year, make, and model of the vehicle. Sometimes the engine size and other factors also make a difference. 

Manufacturer Specific Codes and Data

Unlike generic OBD2 codes and data, manufacturer-specific information is defined by the automaker. Manufacturer-specific diagnostic information can be retrieved from all of the vehicle’s onboard modules, whereas generic OBD2 pertains to the powertrain.

All Model Year 1996 and Newer Vehicles Support Both Types of Codes and Data

Every model year 1996 and newer car will support select powertrain codes and data from both the generic OBD2 pool and the vehicle manufacturer. That means every car has two separate sets of powertrain data: generic and manufacturer-specific.

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An example of a manufacturer-specific engine data list on a 2008 Ford Escape Hybrid.

Every vehicle will support a list of generic OBD2 powertrain live data parameters, which can be retrieved using a generic scan tool. At the same time, there will also be a separate list of powertrain live data parameters defined by the vehicle manufacturer. 

Note: The two images above demonstrate the two sets of data (generic and manufacturer-specific) being retrieved from a single vehicle.

The same holds true for codes. A generic OBD2 code will have two definitions: one from SAE and another from the vehicle manufacturer. Usually, the two definitions are similar or the same but not always.

In many cases, you’ll need access to the manufacturer-specific information to accurately diagnose a vehicle.

The Different Types of Scan Tools and Code Readers

Is your car’s check engine light illuminated? Or maybe the anti-lock brake warning light is turned on?

The type of scan tool or code reader you reach for will determine whether you can retrieve the codes associated with those warning lights. Also, the device you select will play a role in whether you can accurately diagnose the vehicle.

Code Readers

As was mentioned, most code readers are designed solely to read and clear diagnostic trouble codes. But not all code readers are created equal. There are several tiers of code readers, with the most basic tools only being capable of reading and displaying the numeric portion ( e.g., P0420) of currently stored codes.

If you step up to a slightly more sophisticated code reader, you’ll typically be able to retrieve the full generic code definition (e.g., P0420 Catalyst System Efficiency Below Threshold, Bank 1) for current, history, and pending codes.

Some more advanced readers will also display freeze-frame data and OBD monitor status. Usually, you’ll also be able to retrieve manufacturer-specific codes, but they often don’t have a definition beyond the code number.

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An example of the system codes available in a mid-tier code reader when connected to a 2008 Ford Escape Hybrid.

It’s worth pointing out that most code readers only display powertrain DTCs, though some will also display select chassis and body electronics codes.

Generic Scan Tools

A generic scan tool can usually display everything a code reader does, plus generic OBD2 live data. Because such scan tools can only access generic information, you’re typically limited to powertrain codes. There are, however, some generic scanners that can display select chassis and body electronics codes.

OEM-Enhanced Scan Tools

OEM-enhanced scan tools provide generic OBD2 information, as well as manufacturer-specific codes and live data. In addition, most OEM-enhanced tools can retrieve information from all of the vehicle’s modules, ranging from the powertrain to climate control.

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Most OEM-enhanced scan tools allow you to access all of the vehicle’s modules, as you can see in this example while communicating with a 2008 Ford Escape Hybrid.

Many OEM-enhanced tools also provide bi-directional controls, which allow the user to perform operations (for example, turning the electric cooling fan on and off) on select output devices via the scan tool. Some of these tools can also perform more advanced functions, such as key programming and advanced driver assistance (ADAS) calibrations. 

Factory Scan Tools

As you might guess, a factory scan tool is designed to only work on a specific brand of vehicle. Examples include the Ford Integrated Diagnostic Suite (IDS) and the Nissan Consult. These days, most factory scan tools consist of original equipment (OE) software loaded onto a laptop. 

You can often get knock-off versions of factory scan tools online, but they often don’t function as well as the original equipment. Also, black market factory scan tool software can contain viruses.

Which Type of Tool is Right for You?

Now that you know what kinds of scan tools and code readers are out there, you might be wondering which is right for you. The answer depends on your lifestyle and level of automotive knowledge.

If You’re a Do-It-For-Me (DIFM) User

Even if you’re the DIFM type who lets a professional handle all of your auto repairs, you can still benefit from owning a simple code reader. You can stash the device in your car in case the check engine light illuminates. If the light turns on, you’ll be able to retrieve powertrain DTCs and get an idea of what might be wrong with your car before bringing it to the mechanic.

If You’re an Entry-Level Do-It-Yourselfer (DIYer)

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An example of a dash-mounted device that displays generic OBD2 codes and live data.

An entry-level DIYer is generally someone who tackles routine maintenance and small repairs on their car. If you fall into this category, a generic scan tool will likely be a good fit. Such tools offer an affordable way to view OBD2 codes and live data that can shed some light on powertrain problems.

If You’re an Intermediate to Advanced Do-It-Yourselfer (DIYer)

If you plan on only working on one brand of car (for example, Ford), a factory scan tool might be a good choice. Otherwise, an OEM-enhanced scanner that covers a wide range of makes and models is the best choice for an advanced DIYer.

These days, vehicles are so complex that many problems can’t be diagnosed without an OEM-enhanced scan tool. Such a device gives you access to factory codes, live data, and other functions that you’ll need to troubleshoot modern vehicles. 

About The Author
Written By Automotive Subject Matter Expert at

Mia Bevacqua has over 14 years of experience in the auto industry and holds a bachelor’s degree in Advanced Automotive Systems. Certifications include ASE Master Automobile Technician, Master Medium/Heavy Truck Technician, L1, L2, L3, and L4 Advanced Level Specialist. Mia loves fixer-upper oddballs, like her 1987 Cavalier Z-24 and 1998 Astro Van AWD.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

File Under : DIY , For the Car Owner , Maintenance
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Do you have any cod records for a Dodge 350 Diesel it says (DEF ) I changed the DEF pump now I just have to reprogram to reset it


What kind of code reader do you recommend to get that DEF light off and reset it



If you’re talking about performing the “DEF Reductant Doser Prime Override Test”, which is required after installing and new pump on select models, you’ll need either a factory tool or an OEM-enhanced tool with bi-directional controls. If you go with an OEM-enhanced tool, such as one from Autel, Launch, or TOPDON, you can call customer service to ask whether that test is supported by whatever tool you’re considering.

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