What it means
A control module has detected that communication bus F is off. The code does not specify which module or the underlying cause.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
Bus F is the communication network linking the modules assigned to it. The control module monitors valid traffic on bus F; this code sets when bus F is detected as off, without identifying which module or fault caused it.
Common causes
Most likely first.
- Bus-B plus wire broken
- Gateway module routing CAN messages incorrectly
- 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
- Record all codes and freeze-frame data, then check which bus F modules respond and look for related communication or bus-off codes.
- Inspect bus F wiring and connectors, paying particular attention to the bus-B plus wire described for this fault, for breaks, corrosion, looseness, or shorting.
- Check the gateway's bus F status and routing reports and compare them with the modules that fail to respond.
- With power disconnected as directed by the manufacturer, test the bus-B plus wire and the rest of the bus F wiring for continuity and shorts; check termination against the manufacturer's specification.
- If wiring and termination are sound, isolate bus F modules using the manufacturer's procedure to identify a module that is disrupting the network.
Common fixes
- Repair a broken bus-B plus wire or damaged bus F wiring.
- Clean, secure, or repair corroded or loose bus F connectors.
- Repair or replace the gateway if testing confirms incorrect routing on bus F.
- Replace a terminating resistor only if it fails the manufacturer's specification.
- Repair or replace a module confirmed to be taking bus F offline.
Can I keep driving?
Do not rely on vehicle functions that have stopped responding; affected modules may shut down or limit operation. Stop driving if a safety-related function is affected, and otherwise keep trips limited until bus F communication is restored.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.