The Check Engine light on your Ford Crown Victoria indicates a problem with your vehicle's emissions control system. The Check Engine light comes on as a result of the Crown Victoria's computer, called an ECU, generating a trouble code. Once you have fixed the underlying problem, you need to reset the Check Engine light on your Crown Victoria.
Turn the ignition key to the "On" position.
Open the hood and loosen the retaining nut on the negative battery cable clamp.
Slide the clamp off of the negative battery terminal and wait 5 minutes.
Slide the clamp back over the negative battery terminal and tighten the retaining nut.
Verify that the Check Engine light has gone out on the instrument panel.
