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U0067 — Vehicle Communication Bus E Low

Generic OBD-II · all makesNetwork / communication

U0067 indicates a low voltage condition on communication bus E, which is part of the vehicle's Controller Area Network (CAN) system. This code means the bus voltage is below the expected range, often due to wiring faults, poor connections, or a defective module pulling the bus low.

Symptoms

What causes it — most likely first

1. Damaged or corroded wiring/connectors on bus E

Chafed, broken, or corroded wires in the CAN bus circuit can cause a low voltage condition. Connectors with bent pins or poor contact are common failure points.

2. Low system voltage or weak battery

A battery voltage below 12.4V or a failing alternator can cause the bus voltage to drop, triggering the code. This is especially common in cold weather or after extended periods of inactivity.

3. Faulty module on the bus E network

An internal short or failure in a module (e.g., ABS, BCM, ECM, TCM) can pull the bus voltage low. This is often intermittent and may require isolating modules one by one.

4. Aftermarket accessories or modifications

Improperly installed aftermarket electronics (alarms, remote starters, audio systems) can interfere with the bus voltage or create a parasitic draw.

5. Water intrusion or environmental damage

Moisture in connectors, modules, or the wiring harness can cause corrosion or short circuits, leading to low bus voltage.

6. Engine control module (PCM/ECM) failure

While rare, a failed PCM can cause a bus low condition. This should only be considered after thoroughly inspecting wiring, power supply, and other modules.

How it's diagnosed

  1. Verify the battery voltage is at least 12.6V with the engine off and 13.5-14.5V with the engine running. Charge or replace the battery if needed.
  2. Inspect all visible wiring and connectors on the bus E circuit for damage, corrosion, or loose pins. Pay special attention to areas near sharp edges, heat sources, and previous repairs.
  3. Use a multimeter to measure the voltage on the bus E wires (typically CAN Low and CAN High) with the ignition on. Compare to manufacturer specifications (often around 2.5V for each line).
  4. Disconnect modules one at a time while monitoring bus voltage to isolate a faulty module that is pulling the line low. Start with non-critical modules like the radio or door modules.
  5. Check for any technical service bulletins (TSBs) related to bus E issues for the specific vehicle make and model.
  6. If all wiring and modules check out, consider a possible PCM failure, but this is rare. Verify with a known-good PCM or professional network analysis.

Code facts & related codes

SystemNetwork / communication
StandardizationSAE generic — identical on every make
Related codesU0060 — Vehicle Communication Bus D OpenU0061 — Vehicle Communication Bus D LowU0062 — Vehicle Communication Bus D HighU0063 — Vehicle Communication Bus D Shorted U0064 — Vehicle Communication Bus EU0065 — Vehicle Communication Bus E Performanc

Frequently asked

Can I drive my car with code U0067?

It depends on the severity. If the vehicle runs and drives normally, short trips may be possible, but the code indicates a communication problem that could worsen. If multiple warning lights are on or the vehicle behaves erratically, it is safer to have it diagnosed and repaired before driving.

Will replacing the PCM fix U0067?

Usually not. The PCM is rarely the cause of a bus low voltage code. Most often the issue is a wiring fault, a bad connection, or a different module. Replacing the PCM without proper diagnosis is expensive and often ineffective.

What does 'bus E' mean?

Modern vehicles have multiple communication buses (e.g., CAN-C, CAN-I, CAN-E). Bus E is typically a specific CAN bus used for certain systems like body control, infotainment, or diagnostics. The exact assignment varies by manufacturer.

Can a low battery cause U0067?

Yes, a weak or discharged battery is a common cause. The CAN bus requires stable voltage; if the battery is low, the bus voltage can drop below the threshold, triggering the code. Always check battery health first.