Activating a TPMS sensor wakes it up so the tool can read its ID, pressure, temperature and battery. Programming writes the right protocol and ID into a blank programmable sensor so it works on that car. Relearning teaches the car's TPMS module the new sensor IDs and their wheel positions, so the warning light goes off and the readings show correctly.
What does activating a sensor do?
A direct TPMS sensor sits inside each wheel and sleeps most of the time to save its battery. The TPMS tool sends a low-frequency signal that wakes it, and the sensor replies with its ID, pressure, temperature and battery status. Activating every wheel before a tyre job shows straight away whether a sensor is dead, weak or missing, before the tyre comes off.
When do you need to program a sensor?
Only when you fit a programmable (universal) sensor. These leave the box blank, so the tool writes the protocol for that make and model into them. You can either copy the ID of the old sensor, so the car accepts it without a relearn, or create a new ID, which then has to be relearned. A sensor bought for one specific car usually comes ready and needs no programming.
What is a TPMS relearn?
The car's TPMS module only listens for the sensor IDs it has stored. After a new sensor with a new ID is fitted, or the wheels are rotated on cars that track wheel position, the module has to learn the new IDs and positions. Depending on the car, that happens in one of three ways:
- Automatic relearn the car learns the IDs by itself after a short drive.
- Stationary relearn the car is put into learn mode and each sensor is triggered with the tool, wheel by wheel.
- OBD relearn the tool writes the sensor IDs into the module through the OBD port.
What about indirect TPMS?
Some cars have no pressure sensors in the wheels. Indirect systems compare wheel speeds from the ABS sensors, so there is nothing to activate or program: after inflating the tyres to the right pressure, the system is reset from the car's menu or a button, following the carmaker's steps.
What should a workshop TPMS tool do?
Check that it can activate sensors for the makes you see, read sensor status and battery, program the programmable sensors you stock, and run OBD relearns for cars that need them. CSKA supplies the Autel MaxiTPMS TS508WF, which activates sensors, checks the system, programs Autel MX-sensors and runs relearns, and the THINKCAR THINKTOOL Master X2, whose built-in TPMS module activates, programs and relearns sensors.
Questions
Do I need to relearn TPMS after rotating tyres?
On cars whose TPMS shows each wheel's position, yes, so the readings appear on the right wheel. On cars that only show a general warning, the IDs have not changed, so no relearn is needed. Check the carmaker's procedure.
Why is the TPMS light still on after changing a sensor?
Usually because the car has not learned the new sensor ID yet. Run the relearn for that car, or copy the old sensor's ID when programming a universal sensor.
Can one tool program sensors from any brand?
No. A TPMS tool programs the programmable sensors it is built for. The Autel MaxiTPMS TS508WF, for example, programs Autel MX-sensors.
Talk to CSKA
Tell us the cars you service and the jobs you do, and we will suggest the right tool.
WhatsApp +65 9822 2629