Rough Idle 09 Sierra Hybrid Crew Cab HELP!!!

Will_Lock09 · September 22, 2014

I Have a 2009 Sierra Hybrid 6.0L crew cab that has started to idle rough. I took it to the shop and after hooking up to it the codes p0300 and p0302 were given. 300 was for random cyclinder misfire and 302 was cylinder two. I had the number 2 injector replaced and the problem is still there. The guy working on it says he believes it is the ECM (Electronic Control Module). Now I have an appointment set up at a GMC dealearship to have them run tests on the ECM. That is a week from now does anyone else have any ideas as to what it could be?

CapitalTruck · September 24, 2014

Maybe coil pack?

SirManny · September 28, 2014

How many miles are on this truck? I would have replaced spark plug or coil pack first before replacing the injector. I would check those before paying dealer diagnostic time.

Will_Lock09 · September 29, 2014

How many miles are on this truck? I would have replaced spark plug or coil pack first before replacing the injector. I would check those before paying dealer diagnostic time.

145,xxx. I am going to replace the coil pack today and see if that works out.

SirManny · September 29, 2014

Ok if not that then check/replace the spark plug. If that fails then maybe take it to the stealership.

Will_Lock09 · September 29, 2014

Here is a little more information on the problem: The rough idle/shaking feeling occurs when starting up in park while at 1000 rpm or less and also in drive and reverse under 1000 rpm. When driving around town the truck runs fine with no problems. Why would it only occur under 1000 RPM?

Will_Lock09 · September 30, 2014

Ok if not that then check/replace the spark plug. If that fails then maybe take it to the stealership.

Ok so after taking my truck to the dealership today they have dtermined the same injector is still not functioning propely because the previous mechanice put an aftermarket injector in and not an OEM GM injector. Could this be true?

SirManny · October 1, 2014

Its possible. However, most aftermarket parts exceed what the OEM specs. I would want something in writing that states if the OEM injector doesnt fix the problem then Im not liable for the cost of parts and labor. As far as the issue only being noticed under 1000rpm it could because the engine is not under that heavy of a load under 1000rpm and that any rpm above that the engine is under a heavy load and getting more fuel that makes the symptoms not as noticeable