The modulator valve on a 1999 Jeep Grand Cherokee isn't a single, easily identifiable component like a sensor. Instead, the
modulator functions are integrated into the transmission's valve body. Therefore, there's no single "modulator valve" to locate. The valve body itself contains numerous valves, including those responsible for the modulation of shifting pressure and other transmission functions.
To access the valve body, you'd need to remove the transmission. This is a major undertaking, best left to a qualified transmission mechanic. If you're experiencing transmission issues, take it to a professional for diagnosis and repair.
