Tool Briefing: Tackle TPMS Trouble

Tires used to be what they call “easy money.” To this day, they may be simpler to do than many other components on a vehicle, but TPMS sensors have complicated things.

Unlike early systems which used the ABS sensor and were relearned with a click of a button, almost every system available today uses TPMS transmitters attached to vehicle valve stems that transmit data to a receiver, which is interpreted by a module on the vehicle. So TPMS problems can often be complicated, which makes a customer expecting a quick and “easy” tire change dissatisfied.

Proper TPMS service and precautions

It has been said that “one ounce of prevention is worth a pound of the cure.” The same applies to TPMS sensors.

Half the battle with TPMS equipment for the technician is simply not breaking the sensors. Most TPMS sensors use metal valve stems, and when the tire caps are left off, moisture gets between the valve stem and core, making it impossible to get air out of the tire.

So during an oil change service, religiously replace missing caps, and when it's time to do a tire, don’t fight the valve core when trying to take it out. Use a valve stem cap, such as a No. VSC4KT from Snap-on (See Fig. 1), to slowly let the air out when taking the tires off the car.

Some shops will then replace the gasket and other hard parts with a TPMS kit by using a driver and, commonly, a 11mm socket (See Fig. 2). Be sure to torque the retaining nut to spec. It is up to the discretion of the technician whether to simply use an assist arm on the tire machine to push down the side wall of the tire and service the sensor without taking the whole tire off, or to do the whole mount and balance (See Fig. 3).

When a TPMS sensor is serviced this way, it will not require a relearn of any sort. However, if the valve stem or the transmitter itself breaks for any reason and it cannot be repaired using a system like Ken Tool’s reCore (shown above, left) it will have to be replaced.

The “rule of thumb” is that many domestic vehicles will relearn their own sensor values by simply driving, while many imported vehicles will need their sensors relearned to the vehicle using a TPMS diagnostic tool.

The way these tools are used varies, and when not using an OEM TPMS sensor, the ability to program the sensor will depend upon the capabilities of the equipment. Generally, the diagnostic tool will walk the user through relearning the new sensor so the vehicle will recognize it and in other situations the tech will be “cloning” sensor IDs which can be pulled from the old sensor (See Figs. 4 and 5, next page).

Sadly, different manufacturers’ TPMS systems play by different rules, so having the right information is key. Always consult TSBs and repair information. It is wise to make use of information resources, because even luxury vehicles, like the 2007 BMW X5 4.8L in Fig. 6 (next page), may have their TPMS reset quite simply without a scan tool.

2007 Chevy Suburban LTZ 5.3L, no TPMS readings on cluster

So a Suburban rolls into the shop with remotes that do not lock the doors and dashes where TPMS tire pressures should be displayed on the instrument cluster. Generally, GM TPMS sensors (until the 2012 model year) can be relearned by choosing TPMS relearn on the dashboard and adjusting air in and out of the tires while listening for the horn to beep, indicating the sensor is learned. Ironically, the transmitter also can be relearned using buttons on the dashboard.

The problem is that both procedures do not work with this vehicle. After finding TSB 06-03-16-002A on Autodata (see Fig. 7, next page) it calls for an OEM J46079 TPMS tool to reactivate each sensor.

An aftermarket tool with equivalent capabilities can also be used to do the same procdure. However, on this vehicle that procedure did not work. In fact, the sensors would be relearned for a minute and then lose their memory shortly afterwards.

The TSB then requests that the technician reflash the RCDLR. If this does not work, replace the RCDLR module and reflash it. Not so coincidently, the RCDLR also works as the receiver for the vehicle’s remote.

As of July, 2013, all GM reflashing and diagnostics, including the service programming system and GDS2, can be done with a J2534 compliant interface. On this vehicle, using a Drew Tech Mongoose GM II as seen in Fig. 8, the RCDLR was reflashed.

Using the Tech2 software, which is accessible with the Tech2WIN application that can be downloaded from ACDelco’s service website, the remotes were relearned to the vehicle.

With the right TPMS diangnostic and OEM software, this vehicle was diagnosed and repaired.

Tires are not so simple anymore. Reflashing, TPMS tools and even proper tire maintenance all play a role these days.