I have this troubleshooting number for the Nissan, P0325, with the probable causes being a defective knock sensor, check connector and the wiring to the sensor, low fuel pressure, an engine mechanical condition, a failed relay, and/or a throttle control motor relay circuit. I had replaced my engine with a used engine the prior year. While I am not sure what the main issue is, I believe it might be the knock sensor.
If all of those parts have been swapped over from one engine to the other it is possible that one of those parts are the cause considering the engine was replaced and assuming it was rebuilt correctly. If the engine does not have a mechanical issue, the knock sensor may be the most likely cause. I would recommend having your vehicle looked at by an engine professional to determine the cause of your issue.
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