U0047: Vehicle Communication Bus C Performance

What it means

Vehicle communication bus C performance is outside the monitored range. The code does not identify a specific cause.

At a glance

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

How it works

Vehicle communication bus C carries messages among the modules connected to that network. A module monitors whether those messages and the bus signal remain within the expected operating range; U0047 sets when bus C communication performance falls outside that range, without identifying a particular wire or module.

Common causes

Most likely first.

1. Wiring chafed or marginal
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

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 for communication codes and note which modules are missing, then save freeze-frame data before clearing anything.
2. Check the vehicle information and wiring diagram to identify bus C modules, its gateway path, and network termination points.
3. Inspect accessible bus C wiring and connectors for chafing, loose pins, corrosion, water intrusion, or damage that could make the signal intermittent.
4. Use a scan tool to compare which bus C modules respond and whether communication changes as the harness or connectors are gently moved.
5. With power isolated as specified by the manufacturer, test bus C wiring for continuity and shorts, and check termination resistance against the manufacturer's specification.
6. If wiring and termination pass, investigate gateway routing and individual modules using the manufacturer's network diagnostic procedure.

Common fixes

• Repair damaged or chafed bus C wiring and secure it away from rubbing or heat.
• Clean, dry, or repair a loose or corroded bus C connector.
• Correct a bus C termination fault if testing confirms it is outside the manufacturer's specification.
• Diagnose or replace a faulty gateway or bus C module only after its wiring and power and ground connections pass testing.

Can I keep driving?

If only noncritical features are affected and the vehicle drives normally, a short cautious trip may be possible, but multiple warnings or intermittent functions can signal broader network loss. Avoid driving if steering, braking, engine, or transmission functions are affected, or if the vehicle enters limp mode.