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DTC codes / U00xx · Network wiring and bus faults / U0087

U0087Vehicle Communication Bus F - High

U0087 is a generic network code indicating that a control module has lost or degraded communication on Vehicle Communication Bus F, which is a dedicated high-speed data bus used for specific vehicle functions. The module that set the code detected an abnormal voltage or signal condition on the bus circuit, typically a short to voltage or an open in the bus wiring, rather than a fault in any single component on that bus.

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 light
  • One or more electronic features associated with the modules on Bus F may become inoperative, such as stability control, adaptive suspension, or driver assistance systems
  • Intermittent operation of accessories that share the affected bus, especially during cold starts or rough road conditions
  • A no-start condition if the affected bus carries critical powertrain or security data
  • Often no symptoms besides the warning light, with the vehicle driving normally because the fault is isolated to a non-critical bus segment

Common causes, most likely first

  1. A short to voltage on the Bus F wiring, often caused by chafed insulation against a power wire or a faulty module internally shorting bus voltage to battery positive
  2. An open circuit in the Bus F twisted pair, frequently from a broken wire at a connector or a corroded terminal
  3. A failed control module on Bus F that is pulling the bus voltage out of specification
  4. Water intrusion into a connector or module on Bus F, leading to corrosion and high resistance
  5. Aftermarket accessories improperly tapped into the Bus F wiring, introducing voltage or interference
  6. A poor ground connection for one of the modules on Bus F, causing it to back-feed voltage onto the bus

How to diagnose and fix it

  1. Connect a scan tool and record all stored codes from every module to confirm which modules are on Bus F and which are reporting communication faults
  2. Inspect the Bus F wiring harness for obvious damage, chafing, or corrosion, especially near connectors and known rub points
  3. Measure the Bus F CAN (Controller Area Network) high and low voltages with a digital multimeter at the diagnostic link connector (DLC) to check for a short to voltage or an open
  4. Disconnect modules one at a time from Bus F and recheck bus voltage to isolate a module that is shorting the bus
  5. Perform a resistance check across the Bus F CAN high and low terminals at the DLC with the battery disconnected to verify proper termination resistance
  6. Repair or replace the faulty wiring, connector, or module identified in the previous steps, then clear codes and verify communication is restored
  7. If the fault is intermittent, use a graphing multimeter or oscilloscope to monitor Bus F voltage while wiggling harnesses and driving over rough surfaces

Bus F faults that fool good technicians

  • A short to voltage on Bus F is often caused by a module that remains powered after the ignition is off, back-feeding voltage onto the bus and setting U0087 in multiple modules simultaneously.
  • The code does not always mean the bus wiring is faulty; a failed module on Bus F can pull the bus voltage high, and disconnecting that module will restore normal communication on the rest of the network.
  • Aftermarket alarms, remote starters, or dash cameras tapped into the Bus F wiring are a frequent source of voltage interference that sets U0087 without any factory component failure.
  • A poor ground at a single module on Bus F can cause that module to elevate bus voltage, so always check ground integrity before condemning the bus wiring or other modules.
  • U0087 can be stored as a history code after a low battery or jump-start event, so clear the code and verify it does not return before beginning invasive diagnostics.

Can I keep driving with U0087?

If the vehicle drives normally and only the warning light is on, you can usually continue driving to a repair shop, but avoid using features that depend on the affected bus. If the vehicle exhibits a no-start, reduced power, or loss of critical safety systems, stop driving and have it towed to avoid unsafe operation.

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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