High Speed CAN Communication Bus
What does U0001 mean?
The U0001 code means the vehicle's onboard diagnostic system has detected: High Speed CAN Communication Bus. This is a critical severity code.
Common Symptoms
- Check Engine Light and multiple warning lights illuminated
- Multiple systems inoperative
- Dashboard gauges not working
- Vehicle may not start
- No communication with scan tool
Probable Causes (Ranked by Likelihood)
- Open or shorted CAN bus wiring Very High
- Failed CAN bus terminating resistor High
- Water damage to CAN bus harness Moderate
- Failed module pulling down the CAN bus Moderate
Step-by-Step Diagnostic Procedure
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Check for CAN bus activity with an oscilloscope -- normal signal shows 2.5V differential
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Measure CAN bus resistance between CAN-H and CAN-L -- should be approximately 60 ohms
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Disconnect modules one at a time to find a module pulling down the bus
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Inspect CAN bus wiring for damage, especially at connectors and harness junctions
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Check for water intrusion in module connectors along the CAN bus
Frequently Asked Questions
Can I drive with code U0001?
Do not drive. Lost communication codes indicate a module has stopped communicating on the vehicle network. The affected system is completely inoperative.
What causes U0001?
The most common cause is a failed module or a wiring issue in the CAN bus network. Open or shorted CAN bus wiring is the most likely cause. Power supply, ground, and connector issues should be checked before replacing any module.
Is U0001 expensive to fix?
Repair costs range from $100 - $1000 (parts and labor). Wiring repairs are on the lower end, while module replacement is on the higher end. The module may also need to be programmed after replacement.