What does it mean when the check engine light is lit and then after driving it for a while starts to flash..then it will stay lit and start to flash again.

Service Engine Soon

If the Service Engine Soon indicator light stays lit after you've started the engine, the On Board Diagnostics system (OBD) has detected a malfunction of the vehicle emissions control system. Contact your authorized dealer as soon as possible.
If indicator light is blinking, an engine misfire may be occurring, which could damage your catalytic converter. Drive in a moderate fashion (avoid heavy acceleration and deceleration), and have your vehicle serviced immediately.*
The Service Engine Soon indicator light illuminates when the ignition is first turned on (prior to engine start) in order to test the bulb, as well as indicate whether the vehicle is ready for Inspection/Maintenance (I/M) testing.
Normally, the Service Engine Soon light will stay on until the engine is cranked, then turn itself off if no malfunctions are present. However, if after 15 seconds this light blinks eight times, it means that the vehicle is not ready for I/M testing.Check this link out Gary.
https://owner.ford.com/how-tos/vehicle-features/dashboard-instrument-cluster/warning-lamps-and-indicators.html

check the codes by going to a local parts store like orielly autozone or advanced they all do diagnostic checks for free. its something you should have done months ago when the light first came on. however with it flashing it means its a emission problem with your described problem it tells me its a bad catalytic converter remember to also replace your O2 sensor with it

The lights will illuminate for two seconds when the ignition is turned to the on position
The lights will turn on and then off when the engine is started
The lights may come on and stay lit after the engine has started then turns off when the vehicle reaches about 25 mph / 40 kph
The lights may come on during driving but then turn immediately off. - - However, do not hesitate having the computer codes and system checked by your Subaru specialist. Good luck.

P0340 code means "Something" is wrong in the timing...
from CMP (Camshaft Position sensor) to the crankshaft bolt.

Very first thing, verify connectors are clean and shiny.
clear all codes, even hard codes.

Hi there:
When the light comes on, one or more diagnostic trouble codes (DTC) are stored in the engine control module. These DTCs remain even if the light goes out. To address a Check Engine Light problem, the DTCs are retrieved and the appropriate troubleshooting information is followed in order to determine the problem.

The Four Most Common Check Engine Light Scenarios and What to Do:
* The Check Engine Light turns on and off or flickers.
If the Check Engine Light comes on in the city but goes off on the freeway, then the fault is present during city driving conditions. Pay attention to whether or not the vehicle runs or drives any differently when the Check Engine Light illuminates. If vehicle performance does change, drive the car as little as possible and take it to be checked by a service professional as soon as possible. If there is no change in vehicle performance, you can drive home, but have it inspected as soon as possible. In this condition, you run a risk of the vehicle dying or not starting.

* The Check Engine Light comes on and stays on.
If the Check Engine Light illuminates constantly during driving with no noticeable driving or performance problems, there is a permanent fault in the emission control system. When this happens, the computer that controls the emission system usually has a backup program that runs while the fault is present. (These backup programs are often referred to as "limp home" mode programs.) You should get the vehicle serviced as soon as possible, but in most cases, the vehicle will continue to operate, though you run a risk of it dying or not starting.

* The Check Engine Light illuminates, stays on, and there are performance problems.
This means that a vital component of your emission control and engine management system has a serious problem. It usually involves a component or system needed for the vehicle to run at all. In most cases, drive the vehicle as little as possible. In many cases, the vehicle is not safe to drive at all -it could stop or stall out at any moment. It is best to pull over to a safe place and have the vehicle towed to an automotive diagnostician for a thorough inspection and repair.

* The Check Engine Light light comes on and blinks in a steady pattern while driving.
Don't confuse this steady pulsing of the Check Engine Light light (usually one or more flashes per second) with a flicker (see above). The Check Engine Light may stay on steadily or it may flash when the vehicle is accelerated. This is very serious. There is a severe failure of the emission control system that is causing the engine to misfire to the point that the catalytic converter is damaged each time the Check Engine Light flashes. It may mean that the catalytic converter is overheating to the point that it will glow red or, in extreme cases, start a fire on the underside of the vehicle. Immediately pull over to a safe place and have your vehicle towed to an automotive diagnostician for repair. Vehicles can be severely damaged and even destroyed by fire if this condition is ignored for too long.

Hope this helps.

please some specification what motor u have with diesel or what?
When the engine light flash you are driving or before you start the car. And if u can more aether specification. Thank you

Cycle key to on (not start) then off, then on, then off, then back on & leave in on position. Now watch check engine light and it will begin to flash. When it does, it will flash a certain number of times, then pause, then flash some more. Count those flashes and write them down. All numbers will be 2 digits. For example: flash,flash,flash, pause, flash ,flash,flash. will be code 33. Then small pause starts next set of numbers. When you get 5 flashes, pause, 5 more flashes, =55, that means end of message/codes. Do that a couple of times until your sure of the number(s) and get back to me/us and we will be able to help better from the codes.Saves time and money.

Hello I have a 2007 Magnum 2.7L that has code p0302 cylinder#2 misfire seems to have coolant loss but can find no leaks. Recently had another code p0300, so both are active check engine light started flashing but stop and stayed solid. Not driving it. Replaced spark plugs should I replace coils? Any feedback please.

when was yer last tune up and a possible draw to the battery such as glove box stays lit ive seen this or a trunk light will cause the power loss .i hope you get a tune up winter is approaching ..ps if ck engine light is on midas will diagnosis for free

You need to have it scanned for codes. The flashing overdrive light means it has trouble codes that pertain to the transmission.