Topic
Bidirectional tests and coding
A bidirectional tool sends commands to the car: run a fan, cycle an ABS pump, open an EVAP valve. Coding and adaptations change how a module behaves and need care.
Active tests let you check a part without taking it off: command the cooling fan on, close the EVAP vent valve for a leak test, or cycle the ABS pump to bleed the brakes. If the part responds to the command, the part and its wiring are likely fine and the fault is elsewhere.
Adaptations and relearns reset what a module has learned: throttle body relearn after cleaning, idle relearn, injector coding after new injectors, or steering angle calibration after an alignment.
Coding changes a module's configuration, for example after a replacement module is installed. A wrong value can disable features or stop the car from starting, so save the original settings first and keep the battery voltage stable with a charger while you work.
Common mistakes
- Coding a module without saving its original configuration.
- Running long functions on a weak battery.
- Leaving a component commanded on longer than the test needs.
Pages on this topic
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- What is a bidirectional scan tool and do you need oneA bidirectional scan tool sends commands to your car to run active tests and relearns, not just read codes. What it does, examples, and who actually needs one.Explainer
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