U0014 — Problem with medium speed CAN bus communication

The code indicates a communication issue on the vehicle's medium speed CAN bus, which connects various control modules. It appears when the scanner detects abnormal voltage or signal problems on the bus, often due to wiring faults or module failures.

Common causes

The cause is almost always one of a few things. Here they are — U0014 rarely comes from anything outside this list:

• Damaged or corroded CAN bus wiring or connectors
• Faulty control module on the medium speed CAN network
• Poor ground or power supply to CAN modules
• Interference or short circuit on the CAN bus
• Loose or disconnected wiring harnesses

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Inspect and clean CAN bus connectors and wiring
2. Check and secure all related ground and power connections
3. Use diagnostic tools to identify faulty control module
4. Repair or replace damaged wiring or connectors
5. Replace faulty control module if necessary

That is what holds for U0014 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.