P0328

P0328 is knock sensor 1 circuit high - signal voltage above the upper threshold, meaning the sensor is open-circuit, the harness is open, or there is a short to voltage. Cheapest-first: unplug the sensor and measure its resistance. Piezo about 4-5 megohms, resonant about 90-110 kohm; infinite resistance means an internally open sensor. With the sensor unplugged and key on, backprobe the signal wire at the harness side - it should sit at the PCM bias (about 2.5 V on most platforms) or near 5 V depending on calibration. A reading pinned at battery voltage means a short to voltage in the harness. Reconnect, run the engine, and verify with an AC-coupled scope: a healthy sensor produces 20 mV to several hundred mV AC of combustion noise. Caveat: same warning as P0327 - on GM LS trucks the actual fault is almost always under the intake manifold, not the sensor itself, and condemning the sensor first will cost the customer a redo.

Vehicle-specific patterns: 1999-2007 GM 4.8/5.3/6.0 LS trucks set P0328 from the under-intake harness corrosion creating an open instead of a short; same TSB 02-06-04-037 fix. 2002-2008 Honda Civic/CR-V K20/K24 sets P0328 from a cracked knock sensor connector at the back of the block. 2007-2013 BMW N52/N54 has knock sensor wiring that chafes against the intake manifold supports. 2005-2010 Audi A4/A6 2.0T sets P0328 from the rear-bank knock sensor harness pulling apart at the connector. Estimated repair: $80 to $700.