I HAD THE SAME QUESTION AND HERES A LINK TO THE ANSWER http://www.suncoreindustries.com/instructions/40F-30-R+HD.pdf
where is the ignition control module located on mercury marquis
check under the glove box
The air suspension control module is located behind the instrument panel, on the driver's side 'A' post. The control module is attached to the 'A' post with a single screw and two plastic clips.
The body control module, on your 1997 Oldsmobile, is located on the rear suspension. The module is mounted on the passenger side of the rear axle.
The suspension control module (otherwise known as a vehicle dynamics module (VDM)) is located in the trunk underneath the dash of the rear window, almost center, slightly off to the driver side. When servicing this, BE SURE TO TURN THE IGNITION AND THE AIR SUSPENSION SERVICE SWITCH TO THE OFF POSITION. Then you will need to remove the upper trucnk compartment trim panel and lower the module tray. Disconnect the wiring harness jfrom the control module, unsnap the control module from ray clips and remove. Reverse procedure to install.
The sir suspension switch should be located in the front passenger wheel well. It should be there on a Lincoln Continental and most other vehicles with air suspension.
GO to eBay > eBay Motors > place search : For "2004 mercury Grand Marquis Lighting Control Module" , Bunch of listings show up , choose the Lighting Control Module picture that is in WHITE NEW BOX , full instruction ,Where is located ?, step by step removal instruction is all there. The company is ELECTRONICS REMANUFACTURING SERVICE.
The 2003 Navigator suspension module is located under the dash on drivers side above the parking brake pedal.
The wiper control module on a 1998 Mercury Grand Marquis can be found behind the instrument panel. It is close to the steering column, on the right side.
body control module located
It is located above the gas pedal ((about 8") under the dash ,3 connectors from engine side plugs into the module ,the module white sticker part number can be read at the back end of module the number usually starts with 5w...............,that is the module.
The transmission control module and engine control module are one part and are located under the hood.