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Misfiring 2015 GMC 3500HD

darren,smith
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darren,smith New Member

darren,smith

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GMC Sierra 3500 HD 

Codes shown as catalytic operating below efficiency.

Replaced both Cats and all 4 Oxygen sensors...now its misfiring.

Replaced Battery, ran great for the night...then started misfiring again the next morning.

Replaced Camshaft Position sensor...Ran great for 30 min on freeway, sat for 2 hours and started to misfire again....

 

Im at a loss....any hints?

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2016HD Enthusiast

2016HD

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Missfire.. When did you last replace the spark plugs? Plug wires or inspected the coil packs?  Thats where Id look first.  Then possibly injector harness issues or fuel issues. 

 

 

Edited by 2016HD
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