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.
Indicación de gravedad: Alta: detenga el vehículo y diagnostique ahora; riesgo de mayores daños
Síntomas que notará
- Many unrelated warning lamps
- Modules not responding to the scan tool
- No-start or limp mode
Causas habituales
Ordenadas de más a menos probable: empiece por arriba.
- 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
Cómo diagnosticarlo
Primero lo más barato y menos invasivo: la mayoría de estos códigos no son un problema de piezas.
- ✓ 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.
Opciones de reparación
- Repair the shorted or open bus wiring
- Replace the faulty module that is dragging the bus
- Restore the terminating resistor
U0001 — preguntas frecuentes
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.
Confirme el diagnóstico antes de comprar piezas
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