Modern Nissans operate on a Controller Area Network (CAN) bus system. Think of this like a high-speed internet network inside your car. You have the Engine Control Module (ECM), the Transmission Control Module (TCM), the ABS module, and the Body Control Module (BCM). They all share data over this "wire."
Connect your scanner and retrieve all stored codes. Note other U-codes: nissan u1025-00
The ECM checks for CAN heartbeats from the ABS module every few milliseconds. If the module is truly dead or internally open, the code returns instantly (within 1 key cycle). Nissan U1025-00: Decoding the "CAN Comm Circuit" Code
: The vehicle typically enters a reduced power mode ("limp mode"). Severe Power Loss They all share data over this "wire
According to the manual, code U1025-00 indicated a problem with the car's fuel pump control module (FPCM). Specifically, it meant that the car's engine control module (ECM) had lost communication with the FPCM. This code was usually caused by a faulty FPCM, a wiring issue, or a software problem.
Note: Diagnosing network codes often requires professional-grade equipment. If you are uncomfortable with electrical diagnostics, it is best to see a certified mechanic.