Be warned. A single genuine ACDelco knock sensor costs more than that entire listing for two plus a harness. Those are chinese counterfeit ones in bogus GM packaging. They are becoming more and more common too. Check that sellers negative feedback.

 

The ACDelco (213-3521) sensors are made in Mexico. GM (12589867) sensors are made in Germany.
Either will work, they fail due to water intrusion/contact corrosion, not housing corrosion.

 

All I know is they do not all work the same. After pulling my own intake back off 6 months later (zero water intrusion) to replace some cheap ones I'm not going to do that again. That was 5 years ago on my GMC. Also, the cheap ones, the top half separated from the bottom half and would just spin with a socket. That necessitated needing to hammer a chisel into one of them and using pliers on the chisel to get it back out. Then had the exact same issue with my friends Avalanche. He put cheap ones in and less than a year later I helped him replace them a second time. I put ACDelco ones in my H2 and a not a single problem since. I've also personally helped at least two others change theirs and one of them cheaped out and he also had to replace them a second time. So maybe it is a fluke but every time I have personally messed with cheap ones, they had to be replaced again in under a year.

 

Good information. A few things to suspect possible failures:
Over-torque during install.
Replace the connectors/harness as recommended by GM.
Yes, there are Covid-China knockoffs, that have stickers on them.
Made in Mexico or Germany are engraved.