My check engine light appears sumtimes on my dash board. What does that mean, I've just had service and wof and all is fine. Why is this coming on sumtimes

service engine soon ??? This has to do with the vehicles emissions When this light comes on it means your vehicle is polluting 1 & 1/2 times greater then the EPA allows . DTC'S - diagnostic trouble codes are stored in the engine computer . The light is a warning to the driver to take your vehicle to a qualified repair shop.

If it is lit. It is on. It appears on the dash when it is activated.

If the gas cap is tight then rpelace it.

The signal light switch is at fault. I remedied a similar situation in a vintage car by using 4 rectifiers as "back diodes" to block the current flow from the application of the brake lights to the rest of the vehicle. 1N5403 should work fine if you try that approach as opposed to replacing the signal light switch.

There should be defect with sensors. check with engine scanner

cam shaft position sensor at front of engine on top, i ve done a few of them you need to replace it.

Yes it's fine to drive with the service light on BUT it will need a service other wise you could end up with costly repairs due to engine bein neglected

These newer engine are not like the older ones

Sounds like a charging system issue. Just because the alternator itself tested fine doesn't mean it's getting power to the car and battery. Charge the battery and start the car (with everything connected normally, including alternator). While car is idling, disconnect the battery (negative post wI'll do). If car dies, there's a problem with the alternator wiring/harness. Once the vehicle is running, the alternator should provide plenty of power. Check voltage at battery (from alternator) and should be around 14V. Check alternator fuse.
Could be the voltage regulator in the alternator going out, which would need a new alternator.

IT COULD BE A SENSOR GONE BAD , NEED TO HAVE IT SCAN , AJ

that light is the engine warning light you should go and have your car checked over at a garage running very low on oil can cause some serious problems with your engine. you'll also have to go to a garage to get them to turn your light off.