The TPMS light is on, and it is easily isolated to a nail in one of the tires.  You repair the punctured tire, and air all the tires to their correct pressures.  Yet the TPMS light is still on.

Not unusual.  Many TPMS sensors have to be "awakened" before they will transmit their data, and there are a few different ways OEMs do that.  Many will wake up at speeds over 20 MPH, so a drive around the block usually turns the light off.  But there is another way.  Use your TPMS tool to wake them up!

I use the Bartec 400, and have used this method to turn off the light on many models without the drive around the block.  I've also used this method to retrain sensors after a tire rotation or sensor replacement, when the OE procedure calls for either letting air out or using a magnet around the valve.  In those cases, though, I still had to put the vehicles into "learn" mode.

The Bartec tool is also the first tool I grab when diagnosing a TPMS light.  Yeah, I know, check the tire pressures first.  But what if they check OK?  I have had a few rare instances where the sensor was reporting incorrectly, and the control module doesn't know whether it's being told the truth or a lie.  If I read a low pressure tire, it is an easy second step to check the pressure manually to confirm the sensor reading.

It is also a good idea to test all the sensors and look for a lit TPMS light PRIOR to any tire work.  It is infinitely better to identify a failed or weak sensor before the tire is broken down, than to explain to your customer afterward why the TPMS light is on when it wasn't on before.

When removing  the tire, be sure to break the outer bead 180 degrees away from the sensor to avoid damage.  Then remove the locknut and seal, allowing the sensor to fall into the tire.  Remove the sensor and then remove the tire.  Install the sensor last, and use new seals and lock nuts.  They don't require a lot of torque, so be careful.  There are special tools available to insure proper torque.  Use them.

The valves inside the sensor are special as well.  Don't exchange one from a rubber stem for use in a TPMS sensor.

Last tip...don't use tire sealer in a TPMS equipped rim.  If your customer did, replace the sensor...it's garbage once that sealant gets into the sensor air inlet.

Whew....that was a bit more than I originally intended.  Oh well, I've been told that sometimes I don't know when to shut up!