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U0006High Speed CAN Communication Bus (-) Open

An open circuit has been detected in the CAN Low (-) wire of the high-speed CAN bus.

Definition

High-speed CAN requires both wires of its twisted pair to form the differential signal, and an open in the CAN Low conductor disrupts communication for modules beyond the break. The detecting module sets U0006, and unreachable modules are logged with lost-communication codes by the rest of the network. Symptoms depend on the break's location and can include multiple warning lights, inoperative gauges or systems, limp mode, or a no-start.

Common causes

  • Broken CAN Low wire from chafing, rodent damage, or a pinched loom
  • Backed-out, spread, or corroded terminal at a module or inline connector
  • Harness damage from a collision or prior repair
  • Failed splice from an accessory installation
  • Open connection inside a module connector (less common)

Common misdiagnoses

  • Modules replaced for lost-communication codes caused by the harness break
  • PCM replacement without wiring diagnosis
  • Instrument cluster replaced for dead gauges
  • Gateway module replaced when the open is downstream of it

Troubleshooting steps

  1. 1.Identify offline modules with a network scan

    Compare responding versus silent modules against the bus topology diagram to bracket the location of the break.

  2. 2.Check termination resistance at the DLC

    Key off, measure across pins 6 and 14: about 120 ohms instead of 60 indicates one terminator is isolated by an open in the bus.

  3. 3.Continuity-test CAN Low through the suspect segment

    Battery disconnected, check DLC pin 14 to the CAN Low terminal at each silent module; expect under about 1 ohm on a good run.

  4. 4.Inspect connectors and splice packs in the segment

    Look for backed-out pins, corrosion, and broken connector locks, especially in areas recently serviced or exposed to water.

  5. 5.Repair and preserve the twisted pair

    Splice with solder-and-seal or OE crimps and restore the wire twist to maintain the pair's noise rejection.

  6. 6.Rescan and road test

    Confirm all modules communicate, about 60 ohms termination is restored, and no U-codes return.

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