1992 was the very last year of the 740. Wiring colours change over the years. The FAQ reference may only apply to earlier. The common config was a single push-on wire (yes, yellow) to connector 'E' on the back of the dash. HOWEVER... you may be hunting down a non-problem. Fuel injection and cruise tests performed on a stopped car will ALWAYS return a "no speed signal" code.

Check the common stuff. Pull up on brake pedal when engaging cruise. A binding vacuum dump switch will cause pedal to not return fully. Ensure that the hose is still connected to the switch. Do your brake lights work? Thay are part of the safety circuit and the bulb-out will not come on if all bulbs are out.

Vacuum hose from servo (engine) to pump (below master cylinder) - either end could have split. Lastly, with engine off, remove hose from servo and depress diaphragm with two fingers until the throttle is pulled partway open. Place another finger on the rear vacuum port where hose was. While keeping port closed, release the diaphragm and see if it keeps the throttle open. A torn servo bellows will not hold vacuum and will release immediately.