P0325: How to Diagnose & Fix — Knock Sensor 1 Circuit Malfunction (Bank 1)

The Theta II 2.4L and 2.0T GDI engines in 2011-2019 Sorentos can experience catastrophic engine seizure due to machining debris left in the crankshaft oil passages during manufacturing. Metal shavings restrict oil flow to rod and main bearings, causing premature bearing wear and eventual engine lock-up. Over 340,000 Sorentos were included in NHTSA Recall 17V-224. Kia extended the powertrain warranty to 10 years/120,000 miles for affected vehicles and deployed the Knock Sensor Detection System (KSDS) software update to detect early bearing deterioration.

A well-documented failure on first-generation Frontier V6 trucks is the distributor assembly, especially the internal cam/crank angle sensor and bearing wear inside the distributor. Owners report intermittent bucking, random stalling, hard starts, and eventual crank-no-start, often after the engine warms up. Nissan issued service information for distributor-related drivability faults, and owner complaint patterns are consistent across Frontier and related Xterra applications using the VG33E/VG33ER.

On the 1MZ-FE V6 the two knock sensors sit in the valley between the cylinder heads, and their sub-harness bakes there under the intake manifold. The wire insulation hardens and chafes, shorting the signal wire to ground and setting P0325 (knock sensor 1 circuit) and/or P0330 (knock sensor 2 circuit). The ECU responds by pulling timing, so the car runs down on power and mileage with a permanent check engine light. The recurring forum lesson is that the harness - not the sensors - is usually the failed part: owners who replace only the sensors see the code return within days.

The 4.8L, 5.3L, and 6.0L Vortec engines used in early GMT800 Sierra trucks place the knock sensors in wells beneath the intake manifold, where water can collect and corrode the sensors or harness. Owners frequently report recurring check-engine lights, timing retard, and reduced power, especially after washing the engine bay or driving in wet conditions. GM issued service information addressing knock sensor corrosion and revised sealing practices.

The single knock sensor bolted to the top of the EJ block on SF- and early SG-generation Foresters has a brittle plastic/resin housing that cracks after years of heat cycling directly on the block. Once cracked, the piezo element's circuit reads out of range and the ECU sets P0325. The car keeps running, but the ECU falls back to a conservative safe ignition map: owners report noticeably reduced power, sluggish throttle response and a measurable drop in fuel economy. The failure is common enough that many independent shops replace the sensor on any high-mileage EJ Forester showing that code without further diagnosis. A secondary cause is the sensor wiring harness chafing or the connector corroding, so the harness should be inspected before condemning the sensor.