Q: Transmission modulator valve is not working.

Hi there. The modulator valve is located on the back of the transmission on the passenger side. The valve is vacuum controlled. So, before you replace the valve, be sure to check the vacuum line from the engine to the valve and see if there is engine vacuum there. If there is no or less engine vacuum, then change out the vacuum line and retest the transmission shifting. If the transmission shifts, then that was your issue. If the transmission still does not shift, then I recommend replacing the valve. If you need further assistance with your transmission not shifting, then seek out a professional, such as one from Your Mechanic, to help you.