Most beginners start with a simple engine code reader — and that’s fine.
But if you actually want to diagnose problems, test components, or work with different systems in the car, you need a full system scanner.
In this guide, you’ll learn what full system scanners can do, how they work, and why no single scanner is perfect.
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What is a full system OBD2 scanner
Full system scanners are a step above basic code readers.
A code reader works only with the engine, while a full system scanner gives you access to all control modules in the car.
That means you can diagnose:
- ABS
- Airbag (SRS)
- Transmission
- Body modules
- And other systems
Full system scanner vs code reader
| Feature | Code Reader | Full System Scanner |
|---|---|---|
| Engine fault codes | Yes | Yes |
| Live data | Yes | Yes |
| Other modules (ABS, airbag…) | No | Yes |
| Service functions | No | Yes |
| Bidirectional tests | No | Yes |
Connection options explained
Global OBD (basic mode)
Works the same as a simple code reader:
- Reads engine fault codes
- Shows live data
- Displays readiness monitors
👉 Uses standardized protocols
👉 Sometimes shows engine faults that full scan misses
Full system scan (advanced mode)
Connects to all modules in the car:
- Full diagnostics
- Service resets
- Bidirectional tests
👉 More powerful
👉 But also less reliable sometimes
Important: no scanner is perfect
This is the most important thing to understand.
- Not every function will work on every car
- Some modules may not respond
- Some tests may fail
👉 Even if the car is officially supported
Real-world behavior
You can have a situation like this:
- Scanner A → cannot perform test
- Scanner B → connects but fails
- Scanner C → works perfectly
👉 Same car, different results
Practical takeaway
- Start with one good scanner
- Add another tool later if needed
- If something doesn’t work, try a different scanner
Full system scanners are more powerful than code readers, but they require more experience.
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Hi, I am Juraj Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars.
