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U0007High Speed CAN Communication Bus (-) Low

The CAN Low (-) wire of the high-speed CAN bus is stuck at low voltage, typically from a short to ground.

Definition

CAN Low normally idles near 2.5 V and is driven down toward 1.5 V during dominant bits; when the wire is shorted to ground it sits near 0 V continuously, corrupting the differential signal and halting communication on that segment. U0007 sets in the detecting module, usually accompanied by lost-communication codes across the network. Expect multiple warning lamps, inoperative gauges or features, limp mode, or in some cases a no-start.

Common causes

  • CAN Low wire chafed through to chassis ground
  • Water-filled or corroded connector bridging CAN Low to a ground pin
  • Crushed harness from collision damage or improper repair
  • Internal transceiver failure in a module clamping the line to ground
  • Aftermarket wiring error grounding the bus circuit

Common misdiagnoses

  • PCM or gateway module replaced when the short is in the harness
  • Several modules replaced chasing cascade lost-communication codes
  • Cluster replaced for dead gauges
  • Battery replaced for a no-start caused by the dead bus

Troubleshooting steps

  1. 1.Measure CAN Low voltage at the DLC

    Key on, pin 14 to ground: a reading pinned near 0 V instead of about 2.4 V confirms the line is grounded.

  2. 2.Confirm the short with a resistance test

    Battery disconnected, measure DLC pin 14 to chassis ground; near 0 ohms verifies a hard short to ground.

  3. 3.Unplug modules one at a time

    Watch the resistance to ground as each module is disconnected; if it clears, that module's transceiver is internally shorted.

  4. 4.Divide the bus at inline connectors

    If no module is responsible, split the harness at junction points to bracket the shorted physical segment.

  5. 5.Locate and repair the chafe

    Inspect the isolated segment at brackets, grommets, and sharp edges; repair the conductor, insulate, and secure the loom clear of the contact point.

  6. 6.Verify bus health after repair

    Confirm about 2.4 V idle on CAN Low, roughly 60 ohms across pins 6 and 14 key-off, and a clean full-system rescan.

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