HomeTrouble CodesU0015

U0015 — Medium Speed Can Communication Bus Open

Generic OBD-II · all makesNetwork / communication

U0015 indicates the Medium Speed CAN (Controller Area Network) communication bus is open, meaning the bus is not receiving a proper signal from its primary controller.

Symptoms

What causes it — most likely first

1. Faulty Medium Speed CAN controller

The primary controller that drives the Medium Speed CAN bus may have failed, causing the bus to be open.

2. Wiring harness damage

Cracked, frayed, or severed wires in the Medium Speed CAN bus harness can interrupt communication.

3. Connector or terminal corrosion

Corrosion or poor contact at connectors along the Medium Speed CAN bus path can break the signal.

4. Power supply issue to the Medium Speed CAN controller

Insufficient or unstable voltage supplied to the Medium Speed CAN controller can prevent it from functioning.

5. Defective PCM/ECM as a last resort

In rare cases, a fault in the powertrain control module may prevent it from driving the Medium Speed CAN bus, but this is uncommon.

How it's diagnosed

  1. Confirm the U0015 code persists after a reset and during multiple drive cycles
  2. Check the voltage at the Medium Speed CAN controller and its connectors
  3. Inspect the Medium Speed CAN bus harness for visible damage or corrosion
  4. Use a scan tool to test the Medium Speed CAN bus signal integrity
  5. If wiring and power are good, evaluate the Medium Speed CAN controller for failure

Code facts & related codes

SystemNetwork / communication
StandardizationSAE generic — identical on every make

Frequently asked

Is the PCM the usual fix for U0015?

No, the PCM is rarely the cause of an open Medium Speed CAN bus. The issue is almost always a wiring, connector, or controller fault.

Can I just reset the code and it will go away?

Resetting the code will only hide the symptom temporarily. If the underlying fault remains, the code will return after a few drive cycles.

Does this affect emissions?

An open Medium Speed CAN bus can prevent proper sensor data transmission, which may lead to higher emissions or a failure to meet emissions standards.