You got a diagnostic on your Nissan Xterra 2001 P0455 and P0325 What does that mean?

P0325 code is a malfunction in the knock sensor which is designed to monitor piston knocking. When detonation occurs the knock sensor will send a signal to the computer to slow down the engine timing to prevent further damage to the engine. Most of the time the code is due to a defective knock sensor or a faulty wiring connected to the sensor. Once out, the knock sensor can be checked for resistance and compared to a new one.

P0455 deals with your evaporative system which is designed to avoid leaking fuel vapor to the air. It could be caused by any part of the evap system from the gas cap to the purge solenoid. The purge solenoid allows for the flow of gas vapor between the tank, fuel canister and throttle body. When this solenoid is defective, the flow could be disrupted and prevent the circulation of vapors. The most common problem is leakage which can occur at the solenoid, canister, vacuum hoses and especially coming from a loose gas cap. Any leak in the gas flow will be detected by the computer since it controls the purge solenoid by getting the fuel mixture signal from oxygen sensor. To repair, always check the gas cap first and make sure it seals well. Next, visually inspect for vacuum leakage by checking for ruptured vacuum hoses, plug pcv valves or cracked canister. The 0455 can be caused by the 0325 when a gross vacuum leak at the intake manifold leans out the fuel mixture and causes predetonation triggering the 0455. Look where the evap connects to the intake manifold for a cracked or broken hose.