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U0001 U0xxx · ネットワーク (U) 重大度高
High Speed CAN Communication Bus
The high-speed CAN bus is off-line or badly degraded. Multiple modules lose contact at once — which is the clue that tells you it is the bus, not a module.
重大度の目安： 高 — 走行を止めてすぐに診断してください。さらに損傷が広がる恐れがあります
確認できる症状
- Many unrelated warning lamps
- Modules not responding to the scan tool
- No-start or limp mode
主な原因
可能性の高い順に並んでいます。上から順に確認してください。
- 1 CAN-H or CAN-L short to earth, battery or each other
- 2 Open circuit in the bus wiring
- 3 A single module dragging the bus down
- 4 Missing or wrong terminating resistor
点検・修理の手順
費用が安く侵襲の小さい項目から — これらのコードの大半は部品の問題ではありません。
- ✓ Count how many modules are unreachable — more than one means bus, not module.
- ✓ Measure resistance across CAN-H and CAN-L with the battery disconnected: roughly 60 Ω means both terminators are present.
- ✓ Measure CAN-H at ~2.5–3.5 V and CAN-L at ~1.5–2.5 V with the ignition on.
- ✓ Disconnect modules one at a time to find the one that restores the bus.
- ✓ Scope the waveform — a flat line plus one active line tells you which side is shorted.
修理の選択肢
- Repair the shorted or open bus wiring
- Replace the faulty module that is dragging the bus
- Restore the terminating resistor
U0001 — よくあるご質問
How do I tell a bus fault from a dead module? +
If two or more unrelated modules are unreachable, suspect the bus. A single missing module points at that module's supply or wiring.
Why 60 Ω and not 120 Ω? +
There are two 120 Ω terminating resistors in parallel. Reading 120 Ω means one is missing; 40 Ω suggests a third has been added.