HomeTrouble CodesU0032

U0032 — Vehicle Communication Bus High

Generic OBD-II · all makesNetwork / communication

OBD-II code U0032 indicates a malfunction on the vehicle's high-speed communication network, specifically involving the CAN-High circuit. This means the various control modules are unable to exchange data properly due to a wiring fault, a shorted module, or a network termination issue.

Symptoms

What causes it — most likely first

1. Wiring or connector fault on CAN-High circuit

An open circuit, short to power, or short to ground on the CAN-High wire is the most common cause, disrupting network communication.

2. Faulty network terminating resistors

The CAN bus requires specific resistance at each end; if these resistors or their circuits fail, the network signal degrades or fails entirely.

3. Internal short in a control module

A module on the network can internally short the CAN-High circuit to power or ground, taking down the entire bus.

4. Corrosion or moisture in network splices

Water intrusion in connectors or splices where the CAN wires branch off can cause high resistance or shorts on the bus.

5. Failed PCM or ECM

The engine computer is rarely the cause, though an internal failure of its CAN transceiver can pull the network high and trigger the code.

How it's diagnosed

  1. Verify the code and attempt to communicate with all modules using a diagnostic scan tool to see which modules are offline.
  2. Inspect the DLC port and main network connectors for damage, corrosion, bent pins, or moisture.
  3. Measure the network resistance at the DLC port with the battery disconnected to check for proper terminating resistor values (typically 60 ohms).
  4. Use a wiring diagram to locate CAN splices and test the CAN-High circuit for shorts to power, ground, or the CAN-Low circuit.
  5. Isolate a potentially shorted module by disconnecting them one at a time while monitoring bus communication to see when normal operation returns.

Code facts & related codes

SystemNetwork / communication
StandardizationSAE generic — identical on every make

Frequently asked

Does a U0032 code mean my PCM or ECM is bad?

No, it almost never does. Drivers are frequently told to replace the PCM for network codes, but this is usually incorrect. The root cause is typically a wiring fault, a bad connector, or another module shorting the network.

What does 'Bus High' specifically refer to?

It refers to the CAN-High circuit in the vehicle's Controller Area Network. The network uses two wires (High and Low) to communicate; this code indicates the High circuit is shorted, open, or stuck at an incorrect voltage.

Can I drive my car with this code?

It is not recommended. Because the control modules cannot communicate, critical systems like the engine, transmission, and safety features may operate unpredictably or fail entirely.

Can a weak battery cause a U0032 code?

While low system voltage can cause erratic module behavior, it typically sets low-voltage codes rather than a specific CAN-High circuit fault. However, always ensure the battery and charging system are fully functional before diagnosing network issues.