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DTC codes / U00xx · Network wiring and bus faults / U007D

U007DControl Module Communication Bus K Off

U007D indicates that a control module has lost communication on the dedicated bus circuit designated as 'Bus K', which is a manufacturer-specific communication lane within the vehicle's network architecture. The module that sets this code has detected that the Bus K data line is either shorted to power, shorted to ground, or open, preventing normal message traffic between networked controllers.

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

Symptoms you may notice

  • Illumination of the malfunction indicator lamp (MIL) or a dedicated communication fault warning on the dashboard
  • Multiple unrelated warning lights appearing simultaneously because several modules share the affected bus
  • Intermittent or complete failure of features controlled by modules on Bus K, such as lighting, climate control, or body functions
  • The engine may still start and run normally if the powertrain bus remains intact
  • Often no symptoms besides the warning light when the fault is intermittent or affects only non-critical body modules
  • A no-start condition if the affected bus includes the module responsible for immobilizer or starter authorization

Common causes, most likely first

  1. A short to ground or short to power on the Bus K wiring, often from chafed insulation against a metal body panel
  2. An open circuit in the Bus K wiring caused by a broken wire, corroded terminal, or damaged connector pin
  3. A failed control module on Bus K that is pulling the data line voltage out of specification and disrupting all communication
  4. Water intrusion into a connector or module housing on the Bus K network, leading to corrosion and high resistance
  5. Aftermarket accessories improperly tapped into the Bus K wiring, such as alarm systems or trailer brake controllers
  6. A loose or corroded ground connection shared by modules on Bus K, causing reference voltage instability
  7. Internal failure of the gateway module that routes messages between Bus K and other vehicle networks

How to diagnose and fix it

  1. Connect a scan tool and record all stored codes from every module to identify which controllers are offline and confirm Bus K is the common thread
  2. Inspect the Bus K wiring harness and connectors for visible damage, corrosion, or aftermarket taps, focusing on areas near moving components and moisture-prone locations
  3. Measure resistance and voltage on the Bus K data line at the diagnostic connector and at each module connector to check for shorts to ground, shorts to power, or an open circuit
  4. Disconnect modules one at a time from Bus K and recheck communication to isolate a failed module that is dragging the bus down
  5. Repair or replace the damaged section of Bus K wiring, including terminals and connector pins, using proper crimp and seal techniques
  6. Clear all codes and perform a full network communication test to verify that every module on Bus K responds correctly
  7. If a module is confirmed faulty, replace and program it according to the manufacturer's procedures, then recheck for any remaining communication faults

What Bus K faults really tell you

  • A single failed module on Bus K can take down communication for every other module on that bus, so the module that sets U007D is often not the one that needs replacement.
  • Bus K is a manufacturer-defined communication lane, not a standardized OBD-II bus like CAN or ISO 9141, so the exact wire color and pin location vary by make and model and must be confirmed with a wiring diagram.
  • Intermittent U007D codes that appear only in damp weather or after a car wash frequently trace to water intrusion in a connector that looks dry from the outside.
  • Aftermarket remote starters, alarms, and fleet telematics devices are common culprits because installers sometimes splice into Bus K wiring without proper isolation.
  • A weak or corroded ground shared by several modules on Bus K can mimic a wiring short and cause the code to set without any physical damage to the data line itself.

Can I keep driving with U007D?

If the vehicle starts, runs, and all safety systems function normally, you can drive it to a repair shop, but avoid long trips and do not ignore the warning because the fault may worsen and disable additional modules. If the engine will not start or multiple safety systems are offline, have the vehicle towed rather than driven.

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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