U1000 NISSAN GM CODE
THIS IS A MANUFACTURER SPECIFIC NETWORK CODE. SPECIFIC TROUBLESHOOTING STEPS WILL VARY DEPENDING ON THE VEHICLE.
The trouble code U1000 is a vehicle specific code primarily found on Chevrolet, GMC and Nissan vehicles. It refers to a "Class 2 communications failure." Generally, this code will precede an additional code that identifies the module or area of the failure. The second code may be generic or vehicle specific.
U1000 NISSAN POSSIBLE CAUSES
- Controller Area Network (CAN) communication harness is open or shorted
- Faulty Engine Control Module (ECM)
- Poor harness ground connection.
The cause for this code varies with each vehicle. The second code will identify the defective part or area that the fault has occurred. The code is so specific that the technical service bulletins (TSBs) must be examined not only for the make of vehicle, but for the specific model and options present for an accurate assessment. I have experienced several Nissan vehicles with code U1000 that stood alone. No problems were found in any of the systems, yet the code persisted. Exhibiting no driveability or operational problems, the code was simply ignored. Some vehicles direct you to replace the ECM as this is the root cause for this code on this vehicle. Others may lead you to a variable speed wiper motor failure. In the case of one known Nissan TSB, the fix is to clean and tighten the wiring ground connections. The ECM and modules go into a "sleep" mode when the key is off to reduce the load on the battery. Most modules will be go into sleep mode within seconds or minutes after shutdown. The timing is preset and when the ECM commands sleep mode, if the device does not shut down within 5 seconds of the command, even 1 additional second will set this code.
- Engine Light ON (or Service Engine Soon Warning Light)
U1000 CODE REPAIR
All communications through the CAN bus requires a good ground, continuity without shorting, lack of resistance which would cause a drop in voltage and good components.
- Access all technical service bulletins (TSB) relating to code U1000 and any additional codes for your particular model and option group.
- Use the service manual in combination with the TSBs to identify the area or module at fault.
- Study the method to access the faulty module.
- Disconnect the module to isolate it from the CAN bus harness and connector.
- Check the CAN bus harness and connector for shorts or opens using a voltmeter.
- Follow the directions in the service manual used for determining whether the ECM is at Fault or if the module is to blame