Check engine diagnostics



I went to Autozone and had them run the check engine scan.

Are the troubleshooting codes universal to the point if i said them to a car shop they would know what I need or at least what I am talking about?

These are the codes






Code 303 is a cylinder misfire so that needs to be corrected as a first step. (low compression, spark plug, coil, or fuel injector, etc. with the last one not likely)

After that you’re into O2 codes, lean condition, etc. so the first thing I would check for would be a vacuum leak. This can be easily done with a vacuum gauge, which is far superior to the poke and prod method.


Model year? Mileage?


Would you say an engine misfire could stem from me having a remote starter on the car? It has misfired almost everytime I have tried to use it this winter. I have tried to not use it over the two months since I have noticed it but have hit the button on accident a couple of times…Why would it cause such a problem?

When you say “poke and prod” do you mean feeling around till twisting and turning things till I find something?

I really appreciate your response!


122,600(give or take 100miles)


A remote starter should not have anything to do with a cylinder specific misfire.

By poking and prodding, I mean that it can be near impossible to find a vacuum leak if one exists as there are simply too many nooks and crannies where one may exist.
It’s far easier to connect a vacuum gauge to the intake manifold, start the engine, and if a leak appears to be present then start pinching off lines one at a time with a pair of needlenose (old surgical forceps work better) until the leak disappears. That will point you to the problem area, if it exists.

With a misfire there is no sense in worrying about the other codes until the misfire is resolved.
There is always the possibility of a vacuum leak around an injector (O ring seal) so it is at least possible to have a vacuum leak on that cylinder which could then cause a misfire.


As noted, I would chase the other codes before the misfire. I’d clean the mass airflow (MAF) sensor for starters and then check for vacuum leaks and a vacuum gauge is very good for that. If you don’t have one they are not very expensive and are very easy to use.


That code, P0303, means that #3 cylinder is misfiring. Change #3 spark plug. Then, do the vacuum test.