I keep getting the 300, 301,302,303,304 codes. The car will suddenly start running poorly, blinking CEL. I can usually turn the car off for a few seconds, then restart. And, everything is fine for a few weeks. The CEL will usually trun off within a day after the incident. Then a few weeks later, it happens all over again. I don't have a VAG-COM.

Any ideas what it could be?

 

16685
P0301
Cyl.1 Misfire Detected
16686
P0302
Cyl.2 Misfire Detected
16687
P0303
Cyl.3 Misfire Detected
16688
P0304
Cyl.4 Misfire Detected


My best guess would be an Ignition Control Module, since its flipping codes for all these different cylinders. It's around $150-200, so you might want to trouble shoot a little more before you buy one. Look for a loose connection on the coilpacks, and on the ICM.

The ICM is located on top of the airbox, under the cover.

 

Yeah, the ICM seems to be the most likely. I did replace it about 2 years ago though. Is there a way to confirm it is the ICM?

 

You can test all the wires connecting to the coilpacks with a voltmeter to verify they are getting the correct voltage. (search for the correct #'s)

But since your problem is intermittent, this may be dificult to test accuratly. I would check all the connections, and look for any frayed / burnt / exposed wiring. Other than a short, I can cant think of why it would come and go like you mentioned.

Its always difficult when it isn't consistently having the problem.

You may try to search to see if others that replaced the ICM had similar issues as far as it being intermittent.

When mine went, it only was misfiring in 1 cyclinder, and it stayed just in that cylinder. (cylinder number 2 misfire).

Good luck!