1996 Ford Thunderbird Owner's Manual - Page 67

If the light turns on and off on rare occasions while you are driving, it means that a malfunction occurred and the condition corrected itself. An example of a condition which corrects itself occurs when an engine running out of fuel begins to misfire. In this case, the Check Engine Warning Light may turn on and will then set a Diagnostic Trouble Code indicating that the engine was misfiring while the last of the fuel was being consumed. After refueling, the Check Engine Warning Light will turn off after the vehicle has completed three consecutive warm up cycles without a misfire condition occurring. A warm up cycle consists of engine start from a cold condition (engine at ambient temperature) and running until the engine reaches normal operating temperature. On the fourth engine start up, the Check Engine Warning Light will turn off as soon as the engine begins to crank. It is not necessary to have the engine serviced. Under certain conditions, the Check Engine Warning Light may come on if the fuel cap is not properly installed. If the Check Engine Warning Light comes on and you suspect that the fuel cap is not properly installed, pull off the road as soon as it is safely possible and turn off the engine. Remove and replace the fuel cap, making sure it is properly seated. After completing the three consecutive warm up cycles and on the fourth engine start up, the Check Engine Warning Light should turn off. If the light does not go off after the fourth engine restart, have your vehicle serviced by your dealer or a qualified technician. 64