This warning could be on when the engine is running, indicating a fault
has been detected in the system. If left un-repaired, there is a good
possibility that the car will eventually not start.
If the light stays on after trying to start your car or truck and it wont, then
the system needs to be properly diagnosed by a mechanic.
Sometimes a re-learn procedure can be done to get the vehicle to start,
but may not on the next attemp.