U0021

Low Speed CAN Communication Bus (+) Open

Severity

⚠️ Medium

Can you drive?

Yes, but get it checked soon

Approx. repair cost

$6–56 (est.)

Symptoms

Secondary systems do not work or work incorrectly (climate control, audio system)
Multiple related errors appearing on different systems
Check Engine Light Is On
Problems with diagnostics (some modules may not be read)

Causes

Physical damage to CAN bus wires
Short circuit in CAN circuit
Poor contact in module connectors
Fault in one of the modules connected to the bus
Corroded contacts or damaged wiring harness

How to Fix

Visual inspection of the CAN bus wiring harness for damage
Checking the integrity of wires and the quality of contacts in connectors
Diagnostics of resistance and voltage in the CAN bus
Disabling modules one by one to identify a faulty component
Repairing or replacing damaged wires or connectors

Related codes

U0020 U0022 U0023