The 2001 Infiniti Q45 is a luxury sedan from the upscale division of Japanese automaker Nissan. The car is powered by a 4.1-liter V8 engine that generates 266 horsepower and 278 foot-pounds of torque and features a four-speed automatic transmission. If you are having problems driving the vehicle above 40 miles per hour, there are several things you can do to troubleshoot the issue before taking the vehicle in for repairs.
Check that the parking brake is not engaged. A "Brake" light warning will appear in the instrument panel if the parking brake is on. To release the brake, pull the handle on the dashboard above the parking brake pedal. The handle is to the left of the steering wheel.2
Check that the overdrive is set to "ON." When the overdrive is off, a "OD/OFF" indicator light will appears in the instrument panel. If the overdrive is set to "OFF," the vehicle will not shift into the overdrive gear at higher speeds. The overdrive switch is found on the shift lever below the "Shift Lock" button.3
Shift the vehicle into "D" instead of "2" or "L." When the Q45 is in drive, the transmission can shift through all the available gears as the car accelerates. The second and low gears are used for climbing and descending steep hills. These gears will prevent the transmission from shifting out of first or second gear and keep the vehicle from traveling faster than 40 miles per hour.