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P0308 engine code

nickcappy12

By nickcappy12
in Troubleshooting & Recalls

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nickcappy12 New Member

nickcappy12

Posted
Posted

Hello, ive got a 2016 GMC sierra with the 5.3L. Ive had this code P0308 thrown 3 times now and every time the CEL goes off for it its when ive had my cruise control set between 110-120kph on the highway. I feel no loss in power and the truck runs perfectly fine. I just had an oil change done and got my mechanic to replace all the spark plugs and wires and it still came back again. Im starting to think it may have something to do with the AFM because its only happened under light load and at steady highway speeds. Just trying to figure out what the next step would in trying too solve this issue. Any feedback is appreciated 

Buckwild27 Enthusiast

Buckwild27

Posted
Posted
21 minutes ago, nickcappy12 said:

Hello, ive got a 2016 GMC sierra with the 5.3L. Ive had this code P0308 thrown 3 times now and every time the CEL goes off for it its when ive had my cruise control set between 110-120kph on the highway. I feel no loss in power and the truck runs perfectly fine. I just had an oil change done and got my mechanic to replace all the spark plugs and wires and it still came back again. Im starting to think it may have something to do with the AFM because its only happened under light load and at steady highway speeds. Just trying to figure out what the next step would in trying too solve this issue. Any feedback is appreciated 

It takes several times of it happening to keep the cel on. Did you check the compression on the cylinders? 

Also check that the coils are working at full capacity and check for proper fuel psi. 

  • 2 weeks later...
rlcole321 Enthusiast

rlcole321

Posted
Posted

If you can, try swapping coil and wire from cylinder #8 to cylinder #6 and see if it changes to a P0306, since P0308 is misfire cylinder #8), cylinder #8 is not a AFM cylinder, 1, 4, 6, 7 are the AFM cyl.

 

  • Like 1
  • 5 months later...
Steve Poulos New Member

Steve Poulos

Posted
Posted

I've got the same issue, but on a 6.2L. The truck started idling rough and the CEL came on and gave a P0308...changed the plugs, coils, and wires but the light came back. It gave me a P219B so I thought maybe a fuel injector...ran some injector cleaner through it. Didn't work...I changed the MAP and MAF sensors and it still idles rough. I ran a can of Sea Foam through the intake and drove it with "spirited acceleration".  Now it's giving me a P0106 (Manifold Air Pressure Sensor problem). I swapped out the new sensor for another new sensor and it still gives me the same P0106, an occasional P050D and an occasional P0308. Any ideas what I'm chasing? 

newdude Senior Enthusiast

newdude

Posted
Posted
12 hours ago, Steve Poulos said:

I've got the same issue, but on a 6.2L. The truck started idling rough and the CEL came on and gave a P0308...changed the plugs, coils, and wires but the light came back. It gave me a P219B so I thought maybe a fuel injector...ran some injector cleaner through it. Didn't work...I changed the MAP and MAF sensors and it still idles rough. I ran a can of Sea Foam through the intake and drove it with "spirited acceleration".  Now it's giving me a P0106 (Manifold Air Pressure Sensor problem). I swapped out the new sensor for another new sensor and it still gives me the same P0106, an occasional P050D and an occasional P0308. Any ideas what I'm chasing? 

 

 

P050D = Injectors.  I'd do all 8 and don't forget the one time use fuel pipes.  See what happens after that.  

  • 2 weeks later...
Steve Poulos New Member

Steve Poulos

Posted
Posted

Had to trade in the truck. It was deep in the engine and much more than I was willing to pay. Not to mention the transmission was always a PITA. 

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