A bi-directional diagnostic scanner doesn't just receive information from a vehicle—it can also send commands to supported vehicle systems.
This capability is commonly known as bi-directional control or active testing, and it can make automotive fault finding significantly faster.
How Is It Different From a Basic Scanner?
A basic diagnostic scanner can typically retrieve information from the vehicle, such as diagnostic trouble codes and live data.
A bi-directional scanner goes a step further.
On supported vehicles and systems, the scanner can command a component or module to perform an action. This allows a technician to test the operation of a system without relying solely on fault codes.
What Can a Bi-Directional Scanner Control?
Available active tests depend on the vehicle, control module and diagnostic tool.
Examples can include commanding supported:
- Cooling fans
- Fuel pumps
- Injectors
- Relays
- Solenoids
- Windows and door locks
- Lighting
- Electronic actuators
- HVAC components
This can be extremely useful when diagnosing whether a problem is with the component itself, its control circuit or another part of the system.
A Simple Example
Imagine a vehicle has an overheating problem and you suspect the electric cooling fan isn't operating correctly.
Reading fault codes may provide useful information, but with a supported bi-directional scanner you may be able to command the cooling fan to operate directly.
The response to that test gives the technician additional information to help continue the diagnosis.
That is the key advantage of active testing: you're not simply observing the vehicle—you can ask supported systems to perform specific actions.
Who Needs Bi-Directional Diagnostics?
Bi-directional control is particularly useful for professional workshops and technicians carrying out regular fault finding.
It can also be valuable for advanced DIY users who understand vehicle diagnostic procedures and want more capability than a conventional code reader provides.
Does Every TOPDON Scanner Have Bi-Directional Control?
No.
TOPDON offers scanners at different capability levels, so you should check the specifications of the individual diagnostic tool before purchasing.
Vehicle support also varies. A scanner having bi-directional capability does not mean every active test is available on every vehicle.
Always check the specific vehicle and required function before purchasing.
Choosing a TOPDON Bi-Directional Scanner
TOPDON NZ offers diagnostic tools ranging from entry-level scanners through to professional workshop platforms.
If bi-directional control is important to you, look for a scanner specifically offering active-test functionality and confirm coverage for the vehicles you intend to diagnose.