Auto Service Professional

FEB 2018

Magazine for the auto service professional

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Page 47 of 61

46 | ASP February 2018 Technical battery performance. e sensors may be pre-programmed or need to be programmed (depending on make and model of the sensors). e winter tires should feature the same overall diameter as the OE tires in order for the ABS to function, so the winter tires may require the same inflation pressure as the OE tires. If not, the inflation pressure would have to be reprogrammed to the TPMS ECU. Once the wheel and tire assemblies have been installed to the vehicle, the sensors need to be relearned. However. some customers prefer to run different wheels with their winter tires, for two reasons: to save the OE or aftermarket alloy wheels from salt, ice and slush, and for the ability to run a narrower tire with a taller sidewall, which is better suited for snow and ice traction and handling as compared to a wider tire with a shorter and less-compliant sidewall. Tire size would be based on finding a size that is equal or near-equal to the original tire overall diameter in order to provide the ABS module with the proper overall diameter and rotational distance, while being narrower and still providing a load index that is suitable for the vehicle. For example, a vehicle is equipped with OEM alloy wheels and 205/55R16 tires. is size tire features an overall diameter of 24.9 inches. e customer wishes to move to steel wheels and a narrower winter tire with a taller sidewall. One choice would be 15 x 6 or 6.5-inch wheels with 195/65R15 winter tires, which have an overall diameter of 25 inches, but with a narrower section width and taller sidewall. In order for the TPMS to remain opera- tional, TPMS sensors would need to be installed to the new steel wheels, using sensors that have stems compatible with the valve holes in the wheels. Once the sensors are programmed (along with any change to inflation pressure that may be needed), the assemblies are installed to the vehicle and relearned. DO NOT be tempted to install any wheel with no TPMS sensor on any vehicle that was originally equipped with direct TPMS. e National Highway Safety Administration's interpretation of the Motor Vehicle safety Act prohibits service providers from installing aftermarket tire and wheel assemblies without working TPMS sensors. Depending on the state, the TPMS might not need to be functional in order to pass an inspection, but a shop is not allowed to omit the sensors on a vehicle that was equipped with TPMS. From a purely functional aspect, if the winter wheels are not equipped with TPMS sensors, no sensor signal would be sent to the ECM, which will result in no system monitor- ing of tire pressure, and the TPMS warning light to remain on during the months of winter tire use. However, a shop is not allowed to omit the sensors. TPMS module replacement After replacing modules that contain TPMS data, it is required to relearn TPMS data. It's interesting to note that on Ford vehicles, proper module programming and TPMS relearning is required. e vehicle's dome lamp will flash until all needed programming and relearning is complete. Tip for sensor programming e best practice is to program sensors away from where other sensors in your inventory are stored. Multiple sensors might be pro- grammed by mistake. Typically, a flashing TPMS light indicates a TPMS fault and a solid light indicates a tire pressure issue. To make sure that there is not a system fault, cycling the key is necessary. Once driven for a time, the flashing light will go solid. Cycling the key will reset the system and allow for either a solid or flashing light. It's best practice to relearn the TPMS anytime the wheels are removed. You never know if the "last guy" rotated the wheel/tire assemblies and did not perform a relearn.

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