U0016: Medium Speed CAN Communication Bus Off

What it means

The medium-speed CAN communication bus has entered a bus-off state. The affected functions depend on the vehicle network layout.

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

The medium-speed CAN bus carries messages among modules on that network. U0016 indicates the bus has entered a bus-off state, meaning communication has been suspended after repeated transmission errors, commonly due to a wiring fault or a node corrupting traffic.

Common causes

Most likely first.

1. Wiring short forces bus-off state
2. One failing node corrupts traffic
3. Gateway module routing CAN messages incorrectly

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan all modules and save freeze-frame data, bus-off status, and communication codes to identify when the MS-CAN stopped transmitting and which nodes were affected.
2. Check which modules on the medium-speed network are offline and whether their failures began together or after one module reported errors.
3. Inspect MS-CAN wiring and connectors for shorts, damaged twisted-pair wiring, corrosion, or loose terminals that could cause repeated communication errors.
4. Check power and ground at nodes reporting errors before blaming their transceivers, since unstable supplies can disrupt messages.
5. Use the manufacturer's network isolation procedure to determine whether a failing node is corrupting traffic or a wiring fault is forcing bus-off.
6. Check gateway routing after the MS-CAN wiring and connected modules have been assessed.

Common fixes

• Repair a short or damaged section of MS-CAN wiring causing repeated errors.
• Clean and secure corroded or loose network connectors.
• Restore stable power or ground to a module generating communication errors.
• Replace a module only after testing confirms it corrupts MS-CAN traffic.
• Correct gateway routing or configuration if the bus wiring and nodes are sound.

Can I keep driving?

Avoid driving if the fault affects safety-related or essential systems; otherwise limit driving and do not rely on affected body or comfort functions. A bus-off condition can take multiple modules offline, and the vehicle may enter limp mode if critical communication is lost.