ACDelco GM Original Equipment 213-3521 Ignition Knock (Detonation) Sensor

I tried the other sensors (cheap ones) these were the only ones that worked. All of the other knock sensor brands I tried resulted in a low frequency code.

More expensive but worth every penny when they work correctly the first time . This is not a job that u want to do more than once due to cheap parts .

These knock sensors were a direct fit for my 2001 5.3L Chevy Silverado. They were shipped loosely bagged inside the amazon box with some air pillows but arrived undamaged. This is an area of concern that has been discussed however the parts arrived undamaged. One thing to note is that although this is an OEM part, the product is assembled and made in mexico. Upon installation however that did not seem to matter as the sensor performed as it should. These same sensors cost twice as much at the local auto parts store. Amazon had the best value with it being just slightly over another websites price but having two day shipping with prime. The knock sensor performed flawlessly at first start up and its been a week now with no problems. No more CEL :)Some things to note if you are performing the knock sensor job on a GM:Make sure you have an open weekend to perform this job, It will take upwards of 6-8 hours.As noted below, since the manifold will be off, now will be an excellent time to replace optional parts. You might also want to do additional maintenance such as cleaning the IAC, MAF and throttle body.Parts you will need:2 Knock sensors (usually only the rear gets damaged but since this is a large job you might as well swap them both)1 Knock sensor harness (The old one will be useless. The boot wont seal tight and the connectors will be brittle and likely break)1 Intake manifold gasket (This is a given. You do not want to do this and have a vacuum leak after putting it all back together)1 Throttle body to intake manifold gasket (You will problably unmount the throttle body for easier removal and cleaning)1 RTV tube (High temp is preferred. This is used to create a dam and keep water from entering the knock sensor and corroding it)Miscellaneous Optional:1 Bottle of Throttle Body Cleaner (While the whole manifold is off you may take this time to clean the throttle body thoroughly.1 bottle of MAF cleaner (To clean the Mass Air Flow sensor and Idle Air Control Valve)Some Shop Towels: (You will be doing alot of cleaning of parts caked with grease/dirt/grime)Shop Vac:(No matter how careful you are chances are leaves or debris will fall into the cavities of the valves/knock sensor while removing the manifold. A shop vac makes quick haste of cleaning all this debris)Other parts to consider replacing while you have the manifold off:Valve cover gaskets w/grommets(This is a perfect time to replace the valve cover gaskets if you notice any small oil leaks)Heater Hose Quick Connectors:(These things are also notorious for breaking in alot of GM trucks near the firewall. If you have never replaced them, now would be a good time to replace them since you will have easy access to them)Note: I did not include any part #'s as they will vary per vehicle application.

Save your time and money, just shell out for the ACdelco to start with. I learned the hard way. I had to do the job 3 times because I was trying to save a few bucks. Ended up spending more money and spending way more time. DON'T BE LIKE ME!!!!

These sensors did not work in my 04 avalanche 5.3.I bought a pair to replace a rusted out one and went to torque to the 15ft lbs and the top of both sensors spun on me. I tried them anyway and a few miles down the road while watching DTC's, immediately got codes for both sensors. Did a return and replace, got the new set in, same thing. The top spun before it could even be torqued and yet again, a few miles and the codes set again.Bought another pair of ACDelco's from the AZ, this time these torqued fine without the top spinning. Put everything back together thinking I was golden, nope... a few miles down the road again and the codes set.I then bought the cheapest sensors I can get cause at this point I have nothing to lose other then time, however, these gave the same result as the first two sets.Went to the AZ and got their house brand ones and lone behold, these actually work! I've gone 500miles and no DTC and the diagnostic tests actually passed this time.For grins and giggles, I tested the sensors with a oscilloscope multi-meter to look at the AC sine wave and test the resistance. The 3 sets of ACDelco's produced no AC sinewave but resistance was good. The cheap ones produced more AC than the ACDelco's but resistance was around 50k. I got a third sensor, the house brand, from the AZ and I got spikes of AC of around 5V which was a thousand times better than the other sensors and resistance was smack dab 100k.All it cost me was trying 5 sets of sensors and a lot of headache taking the plenum off and on but it comes to show that don't trust just the resistance of these sensors...thats only showing half the picture. Get yourself a cheap oscilloscope multi-meter and test them before you put them in to save yourself the headache. Also I am either bad at the automotive lottery or theres a bad batch of ACDelco sensors out but in the end I am very quick at swapping these out now.

Sometimes it's worth spending the extra cash on AC Delco parts. Considering how huge of a pain in the a$$ it is to replace these on an LS engine, it's money well spent.