2000 Infiniti QX4 P0158 and P0325 Fault Codes: Can They Be Related? Which Should I Fix First?
I recently purchased a 2000 Infiniti QX4 with only 111,000 miles on it. After driving for approximately one hour, the check engine light came on and two fault codes appeared: P0158 and P0325. The vehicle runs smoothly with no noticeable performance issues. I'm wondering if these two codes are related or could be causing each other. Which code should I troubleshoot first? Since this is a relatively low-mileage vehicle, I want to ensure I address the root cause properly without unnecessary repairs.
P0158 (B2S2) indicates that the sensor is not reaching its specified maximum voltage, suggesting a potential issue with the oxygen sensor in bank 2, sensor 2. P0325 (Knock Sensor - KS) indicates a malfunctioning knock sensor. This code typically requires a scan tool to diagnose — you must monitor the actual voltages being received by the Powertrain Control Module (PCM). I recommend prioritizing the knock sensor issue first because if it's active, the PCM will restrict engine timing and performance may drop significantly. Note: A PIA (Part Identification Agreement) part is recommended; aftermarket sensors are often of lower quality and may not meet OEM specifications. Always use genuine Nissan/Infiniti components. Also, it’s important to note that a knock sensor fault might not trigger the MIL (Malfunction Indicator Lamp), so a scan tool is essential to confirm whether the issue is active or just present.