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GM TPMS systems on Buick, Pontiac, Chevy, GMC, Cadillac and Hummer models are some of the easiest to service if you have the right tools and knowledge. Starting in , most vehicles use a TRW-, Schrader- or VDO-manufactured system that all share the same relearn procedures and behaviors, with only a few exceptions (like the Pontiac Vibe).
Shops should use a TPMS tool to reset the sensor positions after rotation. There is a method in the owner&#;s manual to &#;match&#; the sensors that involves deflating a tire for eight seconds.
To see if a code has been set on vehicles with or without a driver information center (DIC), turn the key on without starting the engine, and the TPMS light will blink for one minute and then stay on with a Service Tire Monitor System message. If that occurs, a TPMS system problem exists. On vehicles equipped with a DIC, a SERVICE TIRE MONITOR type message will also display. When the road tire is repaired and reinstalled in the original location, the TPMS indicator icon illumination and DIC message may remain displayed until the DTC is resolved and cleared.
The initial &#;low tire&#; light is similar to the &#;low fuel&#; indicator and adding air to the low tire will extinguish the light. If the driver re-inflates the low tire, they must drive a short distance for at least 30 seconds before the sensors recognize the increase in pressure and turn the light off again. If the deflation is rapid, it will give a more immediate signal by flashing a warning light.
A GM TPMS has pressure, temperature and acceleration sensors. The unit also has a radio transmitter, receiver and battery. Sensors have an estimated 10 year/150,000 mile battery life (GM&#;s estimate). The antenna and receiver are the same as those used for the keyless-entry system. The antenna is typically sandwiched between the layers of glass in the front or rear glass, but some vehicles have a dedicated antenna mounted in various places.
The keyless-entry module communicates with the TPMS sensors and relays the information with the Body Control Module (BCM) on the CAN BUS. If the keyless-entry module or BCM is replaced, the sensors must be relearned. Same goes for the key fobs.
Each sensor has its own unique ID number. If a new sensor is fitted, the BCM must be reprogrammed with its unique ID and its position on the vehicle.
Each sensor takes a pressure measurement sample once every 30 seconds while in stationary mode. If the tire pressure increases or decreases by more than 1.2 psi from the last pressure measurement, another measurement will occur immediately to verify the change in pressure. If a pressure change has indeed occurred, the sensor transmits in learn mode.
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Each sensor has an internal low frequency coil, and when the TPMS tool is used in activate mode, it produces a low frequency transmission that activates the sensor. The sensor responds to a low frequency activation by transmitting in learn mode. When the TPMS antenna receives a learn mode transmission while in TPMS learn mode, it will assign that sensor&#;s ID number to the location on the vehicle relative to the order in which it was learned.
What does it mean to Relearn a TPMS Sensor? When Does it Need to be Done? And How Do I Do It?
Each wheel&#;s TPMS sensor has a unique ID. That sensor ID and associated wheel is registered in the vehicle&#;s TPMS module. When a sensor is replaced or when the tires are rotated, the new sensor ID or the new sensor ID for that wheel location on the vehicle, needs to be registered or relearned to the vehicle&#;s TPMS module.
There are three methods of Relearning TPMS Sensors:
1. Auto Relearn: Driving the vehicle for a specific time and speed.
2. OBD Relearn: Requires a TPMS tool be attached to the vehicle&#;s OBD port to write (Relearn) the sensor IDs to the vehicle&#;s ECU. This procedure is frequently used on most Japanese- and Korean-made vehicles, and Chrysler, Fiat, Land Rover and Jaguar vehicles.
3. Stationary Relearn: New sensor IDs are relearned to the vehicle without the need to drive the vehicle or write the IDs to the vehicle&#;s TPMS module. This relearn procedure should be done in the vehicle&#;s park mode. This procedure is more frequently used on GM, Ford, some Chinese- and Japanese-made vehicles such as Nissan.
To access the stationary relearn mode, you need to:
1. Use the Autel TPMS tool&#;s OBD function to enable the Training or Relearn mode; and/or
2. Operate onboard keys as instructed by your Autel tool. After that, you need to activate all tire pressure sensors to complete the Stationary relearn. Generally, the activation sequence is clockwise, starting from the front left wheel and ending with the rear left wheel.
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