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DTC codes / U00xx · Network wiring and bus faults / U0064

U0064Vehicle Communication Bus E

U0064 is a generic network communication code indicating that the vehicle's computers cannot reliably exchange data on Communication Bus E, which is one of several high-speed data links used for modules such as the transmission control module and stability control. The computer that set the code detected a loss of expected messages or a bus fault on that specific network segment, not a failure of any single sensor or actuator.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaNetwork wiring and bus faults

Symptoms you may notice

  • Illumination of the check engine light, often accompanied by the traction control or stability control warning lamp.
  • Multiple unrelated warning lights on the dashboard because several modules rely on Bus E for shared data.
  • The transmission may default to a limp-home mode with harsh or delayed shifting.
  • Intermittent or complete failure of systems such as anti-lock brakes, stability control, or electric power steering assist.
  • The engine may start and run, but some vehicles enter reduced power mode or refuse to crank.
  • Often no symptoms besides the warning light if the fault is intermittent and other modules retain communication.

Common causes, most likely first

  1. Damaged or chafed wiring in the Bus E harness, commonly at flex points near the transmission, steering column, or body-to-engine mounts.
  2. Corroded, loose, or water-intruded connector pins at any module attached to Bus E.
  3. A failed or failing control module that is pulling the bus voltage out of specification or not transmitting at all.
  4. Internal short or open in the twisted pair of wires that form the Bus E differential pair.
  5. A blown fuse or poor ground that removes power from a module on Bus E, causing it to stop communicating.
  6. Aftermarket electronics improperly tapped into the bus wiring, introducing noise or a short.
  7. Less commonly, a software or configuration mismatch after module replacement or reprogramming.

How to diagnose and fix it

  1. Connect a scan tool that can read all modules and record which modules are online and which are missing from Bus E.
  2. Inspect the Bus E wiring and connectors at each module for chafing, corrosion, water intrusion, and loose pins, starting at the most accessible points.
  3. Measure resistance across the Bus E differential pair with the battery disconnected to check for an open or short, comparing to the manufacturer's specification.
  4. With the bus powered, measure the voltage on both Bus E wires to confirm they sit within the correct high and low ranges and are not stuck or shorted.
  5. Disconnect modules one at a time to see if bus communication returns, isolating a faulty module that is dragging the network down.
  6. Repair or replace the damaged section of harness or the faulty connector, then clear the code and verify that all modules on Bus E communicate reliably.
  7. If wiring and connectors are good, follow the manufacturer's diagnostic flow for module replacement or reprogramming, since a failed module can set this code.

What most technicians miss on Bus E faults

  • A single module with an internal fault can pull the entire Bus E network down, so the code often points to a module that is not the one reporting the fault.
  • Water intrusion into a connector far from the engine bay, such as in a door jamb or under a seat, is a frequent cause that visual inspections at the main harness miss.
  • Aftermarket alarms, remote starters, or dash cameras tapped into bus wiring can introduce the noise or short that sets U0064, and the fault may only appear when that device is active.
  • The code can be stored intermittently from a low battery or a poor ground that causes modules to drop offline briefly, so always check battery health and ground straps before chasing wiring.
  • Bus E is not the same as the primary high-speed CAN bus on every vehicle, so using a generic CAN pinout or assuming the fault is on pins 6 and 14 will send you down the wrong diagnostic path.

Can I keep driving with U0064?

If the vehicle drives normally with only the warning light on, you can drive it to a repair shop, but avoid long trips and towing until the fault is diagnosed. If the transmission is in limp mode, the stability control is disabled, or the engine runs poorly, stop driving and have the vehicle towed because the loss of Bus E can affect safety-critical systems.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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