Hi, This is for someone who curious what the pendullum sensor ( the fifth sensor of 4-channel ABS system ). From Toyota training document, it said the g-force sensor is for 4WD car such as their Celica GT-4 and Camry 4WD. It doesn't explained why it is needed in 4WD cars. But Subaru Legacy 4WD also use this kind of sensor, Audi quattro use 3-channel system so may be it doesn't have it. Ben