Knock sensor code help! P0327 and p0332
Knock sensor code help! P0327 and p0332 I need some help with this as i am stumped. A little background. I just recently replaced the long block with a factory long block from a 04 corvette. The long block swap was straight forward got the car running and its running perfectly only thing is keep getting both knock sensor codes keep coming on. I replaced the knock sensors with 2 new ones straight from the dealer and also a new knock sensor wiring harness also from the dealer. I measured the resistance of the new knock sensors and they were both at 950k ohms within factory specs, the old ones were at 100k ohms also within spec. After replacing the sensors and harness i still get the same 2 codes, nothing changed. I removed the connector at the ecu and i probed the pins that are for the knock sensors and im getting the same 950k ohms i was getting testing the sensors by themselves which means the wiring directly coming off the knock sensor all the way to the ecu is good , so that leaves the ecu? I might add the ecu is a replacement unit. My factory ecu was tuned and it just seemed cheaper to get a replacement as it was only 120 bucks programmed to my car with a factory tune which is what i needed . So my question is can the ecu be causing this? I see a lot of threads of people having this exact same issue but there is no real answer the thread dies off. Any help is appreciated
Joined: Apr 2006
Posts: 3,890
Likes: 1,137
From: Grand Rapids, Michigan
I'm having a somewhat similar issue with my '06 Silverado, but I can't work on it until tomorrow. Installed 2 new knock sensors and the harness, and after about 50 miles the PCM threw a code for knock sensors again. Wouldn't surprise me to have a faulty sensor right out of the box... I have two other knock sensors I can try, so I'll post up what I find tomorrow.
I'm having a somewhat similar issue with my '06 Silverado, but I can't work on it until tomorrow. Installed 2 new knock sensors and the harness, and after about 50 miles the PCM threw a code for knock sensors again. Wouldn't surprise me to have a faulty sensor right out of the box... I have two other knock sensors I can try, so I'll post up what I find tomorrow.
Joined: Apr 2006
Posts: 3,890
Likes: 1,137
From: Grand Rapids, Michigan
Yeah, I did a Google search and there are a TON of posts on various forums about this exact problem. And there wasn't any one specific fix to be had, it seemed. Some people had luck with replacing the sensors, others not so much. The sensors are really delicate, and I'm guessing maybe one of mine got damaged in transit. I will say, the torque spec on these is critical, 15 lb. ft., and I made sure to follow it, but I can't be 100% sure my reading wasn't false due to corrosion in the threads ( iron block ). Might have to chase the threads in order to get it right. It's frustrating, to say the least. Hopefully we both get the problem solved!
So i figured out what my issue was, IT WAS THE $120 PER KNOCK SENSOR FROM THE DEALER!
i ended up pulling the intake for a 3rd time and threw in some 50 buck a piece duralst sensors and problem solved, the codes never came back. Drove over 300 miles and so far so good. Previously it would throw both knock sensor codes immediately after clearing and driving. To anyone that encounters this issue i suggest testing the knock sensors while you have the intake off dont just check resistance because the dealer ones i had checked out, what i didn't check initially is to see if they put out enough millivolts when tapping on the cylinder head or engine block to recreate engine vibrantion. In my case i would say dont buy from the dealer or ac delco buy some that are reasonably priced and check them before putting the intake back on. I just blew $240 dollars on some dealership factory sensors all to do double the work
i ended up pulling the intake for a 3rd time and threw in some 50 buck a piece duralst sensors and problem solved, the codes never came back. Drove over 300 miles and so far so good. Previously it would throw both knock sensor codes immediately after clearing and driving. To anyone that encounters this issue i suggest testing the knock sensors while you have the intake off dont just check resistance because the dealer ones i had checked out, what i didn't check initially is to see if they put out enough millivolts when tapping on the cylinder head or engine block to recreate engine vibrantion. In my case i would say dont buy from the dealer or ac delco buy some that are reasonably priced and check them before putting the intake back on. I just blew $240 dollars on some dealership factory sensors all to do double the work
TECH Fanatic
Joined: Jan 2018
Posts: 1,250
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From: Dade City, Fl.
That is the best way to check the knock sensors. Tapping near the sensor to check if the piezoelectric crystal is actually generating the ac varying voltage(frequency) based on engine vibration intensity
Joined: Apr 2006
Posts: 3,890
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From: Grand Rapids, Michigan
I ended up taking the factory sensors out of my blown up LS1 and stuck them in my truck - Worked perfectly, code immediately went away. Go figure. The quality of these sensors has went downhill big time. Pretty bad that you can't even get good ones from the dealer!
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Joined: Apr 2022
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I’m late to this post, but I’m having an issue with two new (less than 100 miles) knock sensors. I’ve checked from sensor plug to the PCM pins and there’s good continuity. Each sensor, out of the motor, reads 100K ohms (center pin to case). I don’t have a multimeter sensitive enough to read millivolts, but when I tap on the vise holding the sensors, the continuity changes. I’ll be putting in two new sensors tomorrow, but I’m not sold that the CEL is going to go away. The harness is as new as the current sensors and is in excellent shape. If this doesn’t work, can the PCM be checked to see if it’s working properly?
Thanks.
Thanks.
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Joined: Apr 2022
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Thanks. I’ve checked out the continuity from sensor to PCM plug, all sat. I read the resistance on both sensors - 100K ohms. I don’t have a meter sensitive enough to read millivolts, but while connected to read resistance, I tapped (with a hammer) on the vise holding the sensor and the resistance changed. Like I said, I’m at a loss.
The motor had just got its first real tune since a complete rebuild. It’s a 5.3 Vortec with a mild cam, flat top pistons (10:1), 30 lb injectors. The truck had never thrown this code before. I had used mid-grade gas, but on my way home from the tuner, I filled up with regular (87 octane). Could the lower octane possibly cause the code? I didn’t think so because the code indicates a fault with the sensor.
Also, can sensitivity be adjusted through tuning.
Thanks.
The motor had just got its first real tune since a complete rebuild. It’s a 5.3 Vortec with a mild cam, flat top pistons (10:1), 30 lb injectors. The truck had never thrown this code before. I had used mid-grade gas, but on my way home from the tuner, I filled up with regular (87 octane). Could the lower octane possibly cause the code? I didn’t think so because the code indicates a fault with the sensor.
Also, can sensitivity be adjusted through tuning.
Thanks.
It's because all of these older style resonant knock sensors now a days are junk. Resonant sensors are designed for their intended knock frequency so if it's not designed correctly to listen like the factory ones the PCM thinks there is a problem. I have had to turn off those codes on more cars than I can count in the last few years. All of the newer 2 wire flat response sensors don't have this problem since they "hear" everything and it's more up to the computer to filter and listen to the correct frequency.
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Joined: Aug 2025
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It's because all of these older style resonant knock sensors now a days are junk. Resonant sensors are designed for their intended knock frequency so if it's not designed correctly to listen like the factory ones the PCM thinks there is a problem. I have had to turn off those codes on more cars than I can count in the last few years. All of the newer 2 wire flat response sensors don't have this problem since they "hear" everything and it's more up to the computer to filter and listen to the correct frequency.