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2001 GMC Sierra P0327 & P0332 Knock Sensor Low Circuit Voltage Issue - Causes, Fixes, and Best Sensors

Model: 2001 GMC Sierra Fault Code: P0327 Posted: 2015-10-25 19:24

I own a 2001 GMC Sierra Regency Regular Cab with original powertrain mileage reaching 270,000 miles. Previously, I was experiencing lean fuel trim codes (Bank 1 & 2), which led me to replace the intake manifold gaskets. Afterward, the lean codes disappeared—initially a positive result. However, I recently started seeing DTCs P0327 and P0332 indicating low circuit voltage on both Bank 1 and Bank 2 knock sensors. This is concerning because I had replaced both knock sensors and their wiring harnesses (Ac Delco brand) with the expectation of resolving engine performance issues. I suspect over-torquing during installation may have contributed to this problem—especially since I was unaware of the recommended 15 ft-lbs torque specification. Could excessive tightening damage the sensor or its electrical connection? I'm seeking clarity on whether over-torquing causes P0327/P0332, and what steps I should take next. Additionally, I've heard that some knock sensors (especially those from Amazon) are poorly packaged or defective. Could this be a factor in the recurring low voltage readings? Any advice on reliable knock sensor brands or testing procedures would be greatly appreciated.

Related fault codes

P0327P0332

Comments (6)

Anonymous 2015-10-26 15:00

A loose or over-torqued knock sensor can trigger DTCs P0327 and P0332. Try clearing the adaptive memory by disconnecting the battery for a few minutes—this resets the engine control module's learned values, but it does not clear the actual fault codes. This may help reset the system if the issue is related to sensor positioning or torque.

Anonymous 2015-10-27 21:04

I removed the intake manifold again and re-torqued both knock sensors to exactly 15 ft-lbs as per specifications. However, the lean codes returned, and a pending 'Bank 1 low circuit voltage' code appeared on day two. I replaced the wiring harness with a Doorman unit because it was $20 cheaper than the OEM GM version—only now do I regret that choice. The knock sensors were shipped in plain plastic packaging with no protective shielding. While the lean codes may point to an EGR hose leak or misalignment (possibly due to bending during installation), I'm still unsure of the root cause and will continue monitoring the situation. Suggestions are welcome!

Anonymous 2015-11-22 15:23

My 2006 vehicle also shows a 'low voltage to #2 knock sensor' code. I replaced both Bank 1 and 2 knock sensors, but the check engine light remains on. What should I do now? Is there a specific diagnostic step or sensor test that can confirm whether the issue is with the sensor itself?

Anonymous 2015-11-22 16:55

A low voltage reading from the knock sensor indicates it's not functioning properly. To test: disconnect the sensor, set your multimeter to AC mode, insert the positive probe into the sensor terminal, and ground it. Tap the sensor gently—healthy sensors should show fluctuating AC readings. If no variation occurs, the sensor is faulty. I strongly recommend replacing it with a known reliable brand. Avoid Ac Delco knock sensors purchased from Amazon—they have been reported as defective. A Duralast sensor from AutoZone resolved my issue and has performed well so far.

Anonymous 2016-01-20 17:44

After installing a Duralast knock sensor, the lean codes disappeared for several months. However, last week I received a P0327 code again on Bank 2—indicating a return of low circuit voltage. The only working sensor was the original one that remained in place after receiving two defective Ac Delco sensors from Amazon. I suspect I may have damaged the plastic plug on the top of the sensor during reinstallation. The Duralast sensor, despite being warranted, failed under real-world use—highlighting a potential flaw in quality or durability. If anyone has successfully used a knock sensor with a 2001 GMC Sierra LS Vortec engine, I’d appreciate hearing about their experience.

Anonymous 2016-06-16 18:59

I replaced my knock sensor with a Duralast unit and initially saw the P0327 code (originally Bank 2). After replacing it again, AutoZone provided a defective sensor that caused the issue to return. I now have both sensors installed with lifetime warranties and a new full harness from Dorman. I torqued each sensor precisely to 15 ft-lbs—no over-tightening—and reinstalled the intake manifold. The truck started up normally and has run without any issues since. This experience underscores that knock sensors, once shipped, may be defective or compromised during transit. Once installed, they are often non-recoverable and will fail under normal conditions. Always verify sensor quality before installation.