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U0003 Network Communication
High Speed CAN Communication Bus (+) Open
U0003 means the CAN bus high (+) circuit is open. Modules cannot communicate properly over the high speed bus, usually because of a broken wire, bad connector, or loose pin.
🚗 Not recommended. An open on the CAN high wire can take modules offline and cause stalling or a no-start.
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🎯 Top Causes, Ranked by Likelihood
#1 Open CAN high wire $50-$500
A broken or disconnected CAN high wire is the direct cause.
#2 Bad connector or terminal $50-$300
Loose or corroded pins in a connector open the circuit.
#3 Failed module connection $300-$1000
A module with an internal open on the CAN high pin.
🩺 Common Symptoms Multiple modules offline Stalling or no-start Several warning lights Erratic gauges Other U-codes stored 💰 Repair Cost: DIY vs Shop
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🔧 How to Diagnose U0003 1 Locate the CAN high circuit on the wiring diagram
2 Check for continuity along the CAN high wire between modules
3 Inspect connectors for loose or corroded terminals
4 Repair the open and re-scan for codes
❓ Frequently Asked Questions Can I drive with U0003?
Not safely. An open CAN high wire can disable modules and cause stalling. Diagnose it first.
What is CAN high?
CAN high is one of the two twisted wires carrying data on the high speed bus. An open on this wire breaks communication.
What causes U0003 most often?
A broken CAN high wire or a loose or corroded connector terminal.
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