Try adjusting the modulator valve
sorry that's a aod transmission they don't have modulators.the shift is controled by the kickdown cable
You don't mention what year of Mercury Grand Marquis but the owners manual will explain what to do if the transmission gear shift lever will not shift out of ( P / PARK ) with the brake pedal depressed ( it has what Ford calls the " brake shift interlock " ) As of August 6 , 2012 you can still view the Mercury Grand Marquis owners manual online ( back to the 1996 model ) at : www . motorcraft service . com ( no spaces ) Click on Owner Guides
check your brake lights if they not worhing replace fuse or brake light switch
what will fix the overdrive light from flashing in a 1996 mercury grand marquis its a gear ratio problem between 1 and 2 shift
Into Park or out of Park?
Just turn the key to the first position, ( not on ) and then you will be able to shift to neutral and start the car from there. Have the fuses checked and check the shifter sensor on the brake pedal.
Shift solenoids are inside the transmission.
Shift solenoids are inside the transmission, and require disassembly of the transmission to replace.
The transmission shift solenoids are inside the transmission on the valve body.
Ever checked the transmission fluid levels? That can only be checked while the engine is running and at normal operating temperature. The tranny fluid could also be contaminated and need flushing - be sure to change the transmission filter, too.
Stuck in Park? Check to see if the stop lights are working - shift interlock is the same circuit - check the stop light fuse Try to turnthe key to 1st (unlock) position, shift to neutral start vehicle and the shift to Drive
Find the switch attached to the brake pedal for the shift interlock and jump the two wires together. Be careful not to disconnect the brake light switch