Auto Service Professional

FEB 2018

Magazine for the auto service professional

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Page 43 of 61

42 | ASP February 2018 Technical Line systems will display the pressure at each wheel. Low Line systems feature a TPMS lamp that indicates a problem in the system. e applicable sensors are different even in the same model year. General Motors Certain GM vehicles require the use of the key fob or factory tool to put TPMS into the learn mode. Make sure the customer has the key fob and verify that it is broadcasting before starting service. Tips from Schrader/Sensata Technologies e following information is provided by Jacki Lutz at Schrader/Sensata Technologies. "Our call center's number 1 call is always concerning the difference between program- ming vs. relearning a sensor," says Lutz. "Some of our customers don't understand the difference and when instructed to program a sensor, they try to relearn the sensors, causing errors. "Our number 2 call is in regards to relearn- ing the vehicle, in terms of how to relearn the vehicle and the importance of following the unique application instructions to every last detail." Programming and relearning Editor's note: Our intent is not to promote any specific brand of sensor. However, fol- lowing is an example of the steps required to program and relearn an aftermarket pro- grammable sensor. Lutz offers the following advice. Programming: Depending on the aftermar- ket brand and model of sensor, sensors may be pre-programmed or may be initially blank and must be programmed to the specific make, model and year vehicle, with the use of a programming tool. e TPMS tool programs the sensor with the vehicle-specific protocol so that the sensor will communicate with the vehicle's receiver. e sensor can either be created with a new ID or it can be copied from an existing sensor and programmed onto the new sensor. Note that other sensors are available that are pre-programmed and require no in-shop programming and are ready for installation and relearning. Various sensor designs are available from aftermarket manufacturers. Relearning: A relearn is required whenever a new sensor ID is introduced or when the wheel/tire assemblies are rotated. e vehicle's ECU records the sensors (four or five, depending if a spare is in the vehicle). is allows the unique sensor IDs are correctly recognized by the vehicle's ECU. On vehicles with a pressure-by-location function (where the system lets you know which tire is low), the ECU is now ready to display the correct wheel location of each tire's pressure. Using a TPMS scan tool, you're able to relearn the sensor IDs to the vehicle's ECU. e tool will wake up (ping) each sensor, one at a time (LF, RF, RR, LR, spare) and store individual sensor IDs. Reprogramming a TPMS to accept a change in tire pressure must include a new modified placard indicating the supplemental tire cold inflation pressure. In this example, the original placard indicates that the vehicle was originally equipped with 225/50R17 tires with a factory-recommend- ed inflation pressure of 31 psi. The modification placard shows a change to 305/35R24 tires, with an inflation pressure of 41 psi. photo courtesy Bartec

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