U1000: Class 2 communication malfunction / CAN communication circuit
Drive carefully. Get it checked within a week or two.
Can I drive with U1000?
Yes, but drive carefully and get it checked soon. Communication network signal line error common on Nissan and GM; drivable but lights stay on. Meaning can vary by make and model.
What does U1000 mean?
U1000 stands for Solid State Diagnostic / CAN Communication Line - Signal Malfunction.
Symptoms you may notice
- Multiple warning lights on dashboard simultaneously (ABS, CEL, Airbag)
- Speedometer or instrument cluster needles bouncing or freezing
- Transmission may shift harshly or default to safe limp gear
How much does it cost to fix?
Repair costs for code U1000 depend on the specific underlying root cause, ranging from simple DIY checks to component replacement. The table below lists the most common causes and rough price ranges in USD:
- Poor chassis ground connection (especially engine-to-body grounds)
- Weak or failing 12V battery
- Corrosion in harness connectors under the hood
- Failed electronic module pulling network voltage down
What to do next
- Inspect and clean main ground connections on the vehicle chassis and engine block.
- Have battery load-tested at an auto parts store.
- Clear codes once ground terminals are cleaned and tightened.
Last updated: October 2026
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General guidance only, not a professional diagnosis. If the check-engine light is flashing, or the car is running rough, overheating or losing power, stop driving and get help.
About this code
Code U1000 is exceptionally common on Nissan, Infiniti, and GM vehicles. On Nissans, it typically points to a loose or corroded ground strap between the engine block and vehicle frame. Cleaning ground bolts with a wire brush often resolves it.