U0021Controller area network (CAN) data bus: low speed bus (+) - open circuit
Generic (OBD-II) interpretation in the TuningBot DTC database.
U · NetworkNetworkOBD2
What U0021 means
U0021
Controller area network (CAN) data bus: low speed bus (+) - open circuit
Generic · network
Data confidence65%
The control module detected an interruption (open circuit) in the Controller area network (CAN) data bus: low speed bus (+) circuit, so the expected electrical continuity was not present.
Symptoms
Multiple systems may log communication codes
Possible loss of gauge or system functions
Possible causes
Bus wiring open or short circuit
Terminating resistor fault
A faulty node disturbing the bus
Connector corrosion
Recommended checks
Measure CAN-H/CAN-L voltages and bus resistance
Map communicating vs silent modules with a full scan
Generic SAE-standard code: same meaning on every make.
021
Specific fault index within the subsystem.
Frequently asked questions about U0021
What does U0021 mean?
Controller area network (CAN) data bus: low speed bus (+) - open circuit. The control module detected an interruption (open circuit) in the Controller area network (CAN) data bus: low speed bus (+) circuit, so the expected electrical continuity was not present.
Is U0021 generic or manufacturer-specific?
U0021 is a generic OBD-II code: it has the same meaning on every make and model that follows the SAE standard.
Can TuningBot remove U0021 at file level?
Not guaranteed. Powertrain (P) codes can be reliably disabled in the ECU calibration, but body, chassis and network codes depend on the specific control unit and how the fault is implemented - some can be handled, some cannot. Ask for a quote and our engineers will check your file and tell you, free of charge, whether U0021 is removable in your case.
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