Are OBD Scanners Universal? – Read this first!


An OBD scanner is a must have tool for the weekend mechanic. They don’t cost a ton and they’re small enough to fit in your glove box. I’m a mechanic and I used a ton of different models. The capability of scanners does however range from the basic to full dealer level functionality. I’ll share my tips for picking a good scanner.

OBD scanners are universal and will read generic fault codes. Some vehicles however use both generic and manufacturer specific fault codes. Many of the manufacturer specific codes may not be read by a basic universal type OBD scanner.

In this post you’ll learn what a basic scanner can and can’t do, the difference between generic and make specific fault codes. You’ll also learn about the higher end scanners and when you’ll need to use one.

Need to buy an inexpensive scanner that gets the job done, check out the Topdon vs Autel code reader review or, check out the scanners I recommend here on the “Mechanics tools page”.

Universal Scanners

Scan tools

Auto manufacturers must use industry standards when describing their generic fault codes. As a result, plugging even a basic scanner into a Ford, Chevrolet, Toyota, Mercedes will work just the same. In that sense, if you like, we could say most scanners are universal. But as you’ll learn shortly, a basic scanner may not read all the codes.

Scanners are known by other names too, but they all describe the same thing. Some of the names include – Scanners, Code readers, Fault readers, Handheld. 

There’s a ton of scanners on the market that range in price and function. Some users want the ability to just read engine fault codes, others want the ability to test and calibrate components. There’s a scanner for everyone.

Here’s a short descriptor of the main types:

  • Basic code reader – It’s a one directional scanner and reads only industry standard generic engine and transmission fault codes 
  • Vehicle specific – Tool supports wide range of functions and reads all codes but only works on specified make
  • Workshop level bidirectional tool – Multi brand tool with close to dealer level functionality reads all codes

We’ll look at each of these type tools in a little more detail below.

What’s A Generic Fault Code?

Diagnostic trouble codes (DTC) also know OBD2 fault codes or just fault codes is a standard way to identify and categorize vehicle system faults. 

Modern cars have many sophisticated systems, ABS, SRS, MMI, HVAC, Radar etc. and the list is growing. Systems employ sensors and actuators to perform a particular objective. It’s a complex operation and each system is managed by it’s own dedicated control module. (computer)

The control module is capable of self diagnosing, it stores faults codes and arranges them into hard codes (live) and soft codes (historic/intermittent).

To make sense of these codes they are categorized and identified by a letter and four digits. The first character is a letter and it represents a broad system that has registered a fault. 

For example P—-, this represents broadly, a fault somewhere in the powertrain system.

  • P (Powertrain) – Engine and transmission 
  • C (Chassis) – Steering, brakes, suspension
  • B (Body) – SRS, HVAC, Seating, Windows etc.
  • U (Communication) – Module communication network (CAN BUS)

The first digit after the letter denotes the fault as a generic code or manufacturer code.

  • 0 – Generic code
  • 1 – Manufacturer specific

Generic fault codes also known as Global codes, are the industry standard. A fault code such as P0— identifies this fault firstly as a powertrain fault (P) and second, it’s a generic fault code (0). The remainder of the code will identify the nature of the fault.

What’s A Manufacturer Specific Code?

Vehicle specific scanner

Vehicles are not all the same, manufacturers may develop independently, a new system like adaptive suspension, head up display, pedestrian recognition etc. Because many of these systems are only specific to one make, manufacturers categorize and code their own fault codes for these systems.

These codes often aren’t read by the less expensive code readers.

If your code reader does read a specific manufacturer code, you can recognize it from the second character which is most often the number one. For example, P1—.

Basic Code Reader or One Directional Scanner

DTC code reader

One directional scanner, although it can read codes, observe live data and clear codes, its functions are limited. They are typically a small hard case with LCD screen and attached OBD2 cable. A very basic scanner may only have a read and clear function. These type scanners are now very inexpensive and are great for checking your vehicle’s health.

What they can do: A good one directional scanners can perform the following tasks:

  • Read live powertrain faults (Hard codes)
  • Read historic powertrain faults (Soft codes)
  • Check live data readings
  • Clear powertrain fault codes

What they can’t do: 

  • Won’t read or clear Chassis codes (C)
  • Won’t read or clear Body codes (B)
  • Won’t read or clear Communication codes (U)
  • Won’t calibrate components
  • Won’t activate components on command
  • Won’t code control modules

Vehicle Specific Scanner

These are vehicle specific and sometimes model specific. They are available in many forms, handheld devices, software and cable or as an app for your phone.

What they can do: 

  • Read and clear all codes generic and specific
  • Performs calibration/adaption functions
  • Allows for component testing by commanding on and off
  • Employs multi channel waveform in live data and capture
  • Software updates
  • Coding keys

What they can’t do: Full functionality cape abilities.

Workshop Level Bidirectional Scanner

This is a workshop level tool and can perform almost everything a dealer can do. It’s called a bidirectional as it receives info but also allows the user to send commands to the control module. These type scanners are typically a hard case monitor with touch screen and a wireless Bluetooth OBD2 for the car’s data link connector. 

Some scan tools may simply offer a Bluetooth connector and access to their software, using your own laptop.

What they can do: 

  • Read and clear all codes generic and specific
  • Performs calibration/adaption functions
  • Allows for component testing by commanding on and off
  • Employs multi channel waveform in live data and capture
  • Software updates
  • Key coding

What they can’t do: 

Not much they can’t do, programming modules is possible. The limiting factor isn’t the equipment, it’s the access to manufacturer software.

See the high level Autel MaxiCOM scan tool I recommend here on the “Mechanics tools page”.

John Cunningham

John Cunningham is an Automotive Technician and writer on Rustyautos.com. I've been a mechanic for over twenty years, I use my knowledge and experience to write articles that help fellow gear-heads with all aspects of classic car ownership, from tires to roof aerials and everything in between.

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