P0327

P0327 is knock sensor 1 circuit low - the signal voltage or DC bias has fallen below the lower threshold, typically meaning the sensor is shorted to ground, the harness is shorted, or the sensor itself has failed internally. Cheapest-first: unplug the knock sensor and measure resistance across its terminals. Piezo sensors should read about 4 to 5 megohms; resonant sensors about 90 to 110 kohm. A reading near 0 ohms means the sensor is internally shorted. With the connector unplugged and key on, the signal wire at the harness side should sit at a bias voltage (often around 2.5 V) provided by the PCM; if it stays near 0 V, the harness is shorted to ground. On any GM LS truck, before you touch the sensor, pull the intake manifold and inspect the knock sensor harness pigtails for green corrosion - this is the actual fault about 90% of the time on these platforms. Caveat: this is the single most misdiagnosed knock sensor code in the industry. Condemning the sensor before verifying the under-intake harness on GM trucks wastes a $400-700 intake R&R job.

Vehicle-specific patterns: 1999-2007 GM Silverado/Sierra/Tahoe/Yukon/Suburban/Avalanche 4.8/5.3/6.0 LS is THE epidemic platform for P0327 - the foam mat over the lifter valley wicks moisture and corrodes the knock sensor pigtails and the connector at the rear of the engine harness. GM TSB 02-06-04-037 covers the AC Delco wiring harness 12601822 replacement. 2003-2008 Honda Accord/Element K24 sets P0327 from internal sensor failure (Honda part 30530-RAA-A01). 2005-2010 VW Jetta/Passat 2.0T (BPY) sets P0327 from coolant intrusion into the knock sensor connector. 2006-2011 Hyundai Sonata 2.4L Theta II has a TSB for shorted knock sensor wiring. Estimated repair: $80 to $700 (the $700 reflects a full GM LS intake removal plus harness 12601822 plus two knock sensors plus knock sensor foam pad).