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Do knock sensors get "lazy" like O2 sensors?

Babyhauler

By Babyhauler
in Ask A GM Technician

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Babyhauler Enthusiast

Babyhauler

Posted
Posted

Hey guys,

Do the 5.3. knock sensors get lazy and cause lower mileage & performance like old O2 sensors? I usually fill up every 3 to 7 days in my sales job. My 200K, 02 ECSB 2wd had a knock sensor code last year from a wet engine and I had them changed w/ new GM sensors. My mileage showed an increase after this was done. Less than 1 mpg. Peppier driving feel to it also. No O2 code, but I changed the front O2's a month or so later & started bumping 20 mpg a few tanks. Best had been about 18 w/ high avg around 17.5. I went from Jan to May and only went below 15 mpg 2 or 3 times. It used to drop in the low 14's regularly & 13's occasionaly. So I was happy with changing these parts out. Plugs had about 75k on them.

 

My "new" 05 Crew Cab 5.3, 3.23, has only "193K" on it. Lots of maintenace records with tranny, fuel sys, PS, brake fluid, & diff fluid changes and flushes more than needed. In town driving with heavy AC use & I am in the 13.5 range. Quick glance at my records looks like a 14.5 avg overall driving the same areas & 1 hour one way trips to local towns. I changed the O2 sensors 8-10 tanks back on the 05 & I am not getting any improvement like the 02 truck showed. I pulled a few spark plugs & they look good. Not sure if the wires are original or if they matter unless causing a code.

Back to my my original question, do the knock sensors get lazy over time or are they only "bad" when they code? Based on my 2 trucks with similar mileage & records that show a mpg increase with new sensors, I would say they get lazy. Do you have any feedback from your customers about knock sensors? Does GM provide a service interval for the knock sensors?

 

Thank you for your help.

Babyhauler

Carder09 Senior Enthusiast

Carder09

Posted
Posted

I assume you haven't seen any codes on your 05 yet? Codes are stored and the check engine light can go off while you still have the problem. Best thing would be to get those codes extracted from a dealership or a mechanic

Babyhauler Enthusiast

Babyhauler

Posted
  • Author
Posted

No codes at all on the 05.

There were no O2 codes on the 2002, but new ones sure made a difference.

I'm just wondering if I need to change them (knock) due to their age and mileage. They are an integral part of the fuel & ignition

systems and I am sure it all has to work together for the best power and economy.

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

If they got "lazy" they would be slow in reacting to a ping. Doubt that would change mileage, and if it did, you may actually get slightly better mileage.

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