U0002: High Speed CAN Communication Bus Performance

What it means

Performance of the high-speed CAN communication bus is outside the expected range. The code does not identify the cause or the affected functions.

At a glance

• Usually lights the warning light of the system that lost communication

How it works

The high-speed CAN bus carries messages between control modules over paired wires. U0002 means bus communication performance is outside the expected range, such as from disrupted or inconsistent messaging; it does not by itself identify the cause or affected functions.

Common causes

Most likely first.

1. Wiring or connector fault
2. Fault in a connected control module
3. Electrical interference

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 every module that can be reached and note communication codes, missing modules, and whether faults are current or stored.
2. Review freeze-frame or event records for when the bus performance fault occurred and whether it coincided with other electrical symptoms.
3. Inspect the high-speed CAN wiring, connectors, and recent repair areas for corrosion, loose terminals, chafing, or damage.
4. Check battery condition, charging voltage, and relevant module grounds for instability that could disturb communication.
5. Follow the manufacturer’s CAN performance test procedure to check bus signals and isolate a wiring branch or module causing abnormal communication.

Common fixes

• Clean and secure a loose or corroded CAN connector.
• Repair damaged, chafed, or poorly joined high-speed CAN wiring.
• Correct unstable module power or ground connections.
• Repair or replace a module only after testing confirms it is disrupting bus performance.

Can I keep driving?

If warning lights accompany loss of essential functions or unpredictable engine behavior, stop driving and arrange assistance. If the vehicle remains fully controllable and only nonessential functions are affected, limit driving and avoid trips where a sudden loss of communication could create a hazard.