#CAN Bus
8 posts in Car Diagnostics blog about "CAN Bus" — OBD-II diagnostics, DTC codes, repair. ← All posts
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The 60 ohm test: checking CAN bus termination with a multimeter
One measurement, two wires, thirty seconds. It tells you whether the vehicle network is physically intact before you diagnose a single module.
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Speedometer stopped: sensor, cluster or bus
A dead speedometer takes cruise control, the gearbox and sometimes ABS with it. What else stopped working tells you where the fault is.
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U0073: control module communication bus off — the whole network went quiet
This is not one module failing to answer. It is the network itself shutting down, and the cause is usually one device dragging everything else with it.
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U0126: lost communication with the steering angle sensor module
Stability control needs to know where the steering is pointed. Lose that message and several safety systems switch themselves off together.
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U0401: invalid data received from ECM — a message that arrived and made no sense
Not a lost connection. The message arrived intact and its contents were implausible, which points somewhere different from a wiring fault.
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U0101: lost communication with the transmission control module
U0101 means the engine ECU stopped hearing the gearbox module on the CAN bus. The module is often alive and well — it is the wiring, power or bus termination that failed.
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U0121: lost communication with the ABS module
When the ABS module goes quiet, wheel speed disappears from the whole car. Three warning lights come on at once and half the driver assistance systems switch themselves off.
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CAN Bus for car owners: how the "nervous system" of a car works and why it matters for diagnostics
Plain-English CAN Bus: how 60+ ECUs communicate over 2 wires, what ISO 15765-4 and ISO-TP are, high-speed vs low-speed CAN, and why "lost communication with ECU" (U0100+) is critical.