2010 hhr lt trouble code po302 and p0300
 

Ok, REALLY NEED HELP , I HAVE A 2010 HHR LT WITH TROUBLE CODES PO302 AND P0300. I HAVE PUT NEW SPARK PLUGS IN , A NEW COIL, AND COIL WIRE CONNECTOR , EVERY THING THE DEALER SAID NEED TO BE DONE FIRST TO RULE OUT ANY OF THOSE POSSIBLE ISSUES. I STILL HAVE THE SAME CODES POP UP AFTER A FEW DRIVES AND IT SEEMS TO COME BACK WHEN THE CAR IS AT IDLE, PLEASE ANY HELP WOULD BE GREAT , I AM RUNNING OUT OF IDEAS.

Welcome to the site, first lets take off the caps lock, have a look at this video, Please watch it all, and maybe the part about the battery will be the key to this problem.
Also the ground connection at the front of the transmission to the rad cradle up by the front of the engine bay on the drivers side.




I sure hope this helps, now on a 2010 that's roughly 4 1/2 to 5 years old for the original battery, please have it checked out at your local AZ or O'R auto parts store.
I do mean fully checked out, load test and all, these HHR's tend to react funny when not dealing with a full charge

Thank you Oldblue , i have done all that
 

Oldblue , i have a new battery , new spark plugs , coil in cylinder 2 , checked all hoses and all seem fine, i can say that i did have a problem with the ground on the battery where it has a problem starting so i checked the battery and the ground was lose , but i fixed it and again it is a new battery and the problem is still happening . The only thing i have not tried that you suggested was the ( the ground connection at the front of the transmission to the rad cradle up by the front of the engine bay on the drivers side.) i dont know where to check for that , do you have a picture or diagram i can look at , i am willing to try anything at this point, thank you again for all your help

I suggest compression and leakdown testing. If that is clean look at injectors.

The p0300 will go away once the #2 cylinder stops misfiring (p0302).

Ok , now you didn't say about the new battery in your first post, that's OK , now this needs to be done after you have gone into the spare tire area and disconnected the ground wire to avoid any sparks, shorts or computers toasted. place a towel over the rear hatch latch so if you do close the lift gate it won't lock you out.
Oh, you would be surprised. how often I've seen that done

now, open up the hood and look for a 10mm nut up front on the rad cradle on the drivers side, make sure it is clean and tight, now follow it down to the front of the transmission just below and to the drivers side of the oil filter cap. this should also be clean and tight.
under the hood again look for the fuse box , take the cover off, ensure the two halves are tight they are 10mm bolts, the positive connection on the left side of the box is a 13 mm nut, make sure it is clean and tight.
I don't have a picture here on my PC and it's 8 degrees out there today up here, so I do apologize for that, I'm sure you will find these points.

Now tighten the positive cable first back at the battery and then the negative cable , again to avoid a short , spark or have no-panS burned into the palm of your hand.

thread moved to the more appropriate Problems/Service/Repairs forum.

hahahha , i got you
 

I see , and i will check those cables , thanks for the detail description on the location of them. I also saw on another forum that because the symptoms sound the same as " it seems to get those code after driving a while or at idle for a while" and after doing all that i did , said to do a compression and leakdown testing. So after i check the wires and if they are all good then i will take it to the dealer and have them do the testing since i still have warranty on powertrain since i only have 96000 miles on it, so if there is an issue, it should be covered . Thank you very much for all your help

Welcome! If it is under warranty , and just for fun swap out #2 plug and coil for #4 plug and coil pack and see if the code changes to P0304, you can get the codes checked mostly for free at AutoZone or O'reilly's like parts stores.

Saw on another forum? Maybe it was in Post #4 in this thread?

It very well could be , but let's check things out and ensure the problem gets fixed.
I'd suggest compression test and leak down test after the simple things are checked, redundant as they may seem.

I just left it a the dealer
 

I did swap coil , and just so everyone knows , the firing sequence is (1342) i found that out the hard way and after talking to a main tech because every forum and people at the dealer said it was (1234) and its not. I will see what the say after doing another diag and let everyone know whats going on , it seems a lot of people have the same issues with there abs - ecs lights also coming on with this same issue. I will be intouch to let everyone know whats up. Thanks

What difference does the firing sequence make?
Are you confusing that with the numbering order? That is #1 passenger side (front of the engine) #4 driver side 1,2,3 4.

Here's the facts: p0300 means random misfire, p0302 means cylinder #2 misfire. If you have a consistent misfire in any one cylinder, the computer interprets a "random" misfire.

So, if the only cylinder that is misfiring, after a coil swap and plug change is #2 (the one next to #1 at the front of the engine) it's not really a random misfire.

The problem is in cylinder #2 (period). QED.

If you had a bunch of other codes also I would be thinking electrical connections.
But, in this case I am betting something more serious like; burned valve, leaking head gasket, bad injector etc. Thus, the compression and leakdown suggestion.

Never hurts to check the simple stuff! But don't put blinders on.

But eliminate the easy tests then move to the next steps codes can be tripped by a number of things, one being battery condition and connections

donbrew
 

So are you saying donbrew, that even though that the firing order is (1342) that cylinder 2 misfire is still the 2nd chamber from the left when standing in front of the car ?

Yes, that is exactly what he means.

Got it
 

So, i am just going to have the compression and leak down test done because it sounds like a lot of people have the same problem and i really dont think its the connector and if the test comes back that the engine is sound , at least i can rule out any power train issues and not worry about the warranty issue anymore, and that is worth $180.00 to me. I will let you all know what happens

Fingers crossed!

Another simple thing to eliminate:
Make sure the throttle plate is not dirty (sticky-gummy). it WILL cause a RANDOM misfire at IDLE....

Very good point!! And simple to clean !

Confusing cylinder location with firing order. That is a new one on me.