U0007 — High Speed CAN Communication Bus (-) Low

U0007: High Speed CAN Communication Bus (-) Low — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

High Speed CAN Communication Bus (-) Low. Basic catalogue definition; diagnostic details have not yet been reviewed.

Affected system: Network communication

Symptoms

  • Several warning lights or unrelated codes appearing together
  • A module is missing from the scan-tool network list
  • Intermittent no-start, no-shift, steering, braking, or comfort-system operation
  • Functions may return after cycling the ignition

Possible causes

  • Low battery voltage, unstable charging voltage, or poor module ground
  • Open, shorted, corroded, or damaged CAN bus wiring
  • Blown fuse, failed relay, or missing power/ground at the named module
  • A module holding the network down or failing internally

What to check

  • Save the full-vehicle scan and note current versus history codes
  • Stabilize battery voltage and check fuses, powers, grounds, and recent repairs
  • Identify the network and the module that cannot be reached
  • Inspect the shared bus and isolate branches only as directed by service information
  • Restore communication, clear secondary codes, and verify all modules remain online
  • Perform a complete module scan before clearing any codes
  • Verify battery condition and module powers and grounds
  • Compare which modules report the communication fault and which module is absent

Also written as: U0007-00, U000700, UO007 (some scan tools add the fault-type byte, e.g. -00).