Join Date: Oct 2011
Location: Magnetic Hill, New-Brunswick
Okay, I don't want to down what others said that led you to do what you did, but You didn't eliminate anything with the method you chose. Let me explain. By changing the plug and coil for new ones might sound like a good idea and we all assume that new means it is going to work for sure. We all know that ain't true. Now unless you kept the old parts you can't go back. So I'm going to write this for others that might have the same problem. What you need to know is which part is defective so instead of putting in new parts at random and think you eliminate that piece automatically, here is what you need to do. Since pistons 1&4 work or cycle opposite each other and 2&3 do the same what you should have done is take the plug from cylinder 3 and switch it with a known good plug like 1 or 4, this way after clearing the code and P0303 comes back you know it's not the plug. Then do the same with the ignition coil, if the code comes up P0301 you know you have a bad coil, if it comes up P0303 again you leave it cause that means all your plugs and coils are good and you haven't spent a penny yet. Next move on to injectors and do the same switch injectors between 3 and 1 or 4 , P0303 comes back you have eliminated all these parts at no cost yet leaving you with ECM continuity between coil and ECM connectors. Clean connectors and test again. After all this if P0303 is still present you move on to compression test.
---------- Post added at 10:28 PM ---------- Previous post was at 10:13 PM ----------
By the way for some unknown reason when ECM loses cam-crank correlation for a fraction of a second and doesn't know if it's a faulty crank sensor or faulty cam sensor it sets P0303 code on 07-10. GM techs still don't know why according to bulletins. If it fails for longer, then of course it will give a crank or a cam code. Just so you know.
---------- Post added at 10:33 PM ---------- Previous post was at 10:28 PM ----------
My guess you will find that light blue wire on pin "23" of "P2" rubbing on a metal surface somewhere between ECM and ignition coil #3. Just a guess.
Never drive faster than your guardian angel can fly
Last edited by Coby7; 06-23-2013 at 07:47 PM.