The knock sensors in my truck need replacing. The truck has 178K miles (2004 GMC Sierra 2500 non hd crew cab 4wd). I haven't had the truck very long and I'm fixing things as I go. But I just got back from a trip into the mountains and this thing was a dog in the hills with no load at all behind it. I do occasionally pull my 20ft long trailer with 3-4 atvs on it, and I do notice it sucks at times pulling it. I towed the same load with my dad's 5.3 1500 and it pulled better than my truck, especially starting out.

I've searched and haven't found a solid answer on this..but does the knock sensors not working reduce the power output? The reason I'm asking is I have a 2004 6.0 shortblock with 799 heads, and 212/218 cam I'm putting together. I'm wondering if the current power loss is related to the sensors not working (among others not working as well) or is the engine just worn out due to lack of maintenance by the previous owner and I'm better off putting money in the other engine.

 

If there's a knock sensor code stored in the PCM, then yes, it will cause a loss of power. The PCM pulls a ton of timing so it will run "safely" when there's a knock sensor code stored.

 

It runs alot better with the knock sensors replaced. It don't lug around like it did before.