What it means
The vehicle bus reports loss of communication with smart cooling fan 3 (PWM brushless fan with own controller). Fan speed cannot be commanded; cooling falls back to default operation.
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
Cooling fan 3 is a brushless fan with its own controller that receives speed commands over the vehicle network. U067C sets when the control module loses communication with fan 3, so it cannot reliably command that fan and cooling may fall back to a default strategy.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module failed
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
- Scan all modules for communication codes and save freeze-frame data, then check coolant temperature and any fan-related live data.
- With the vehicle safely parked and the engine cool, inspect fan 3's connector and harness for loose connections, corrosion, heat damage, or chafing.
- Identify fan 3 from vehicle service information and check its fuse, power, and ground against the manufacturer's specification.
- Check whether fan 3 responds to a scan-tool command if the vehicle supports that test, and compare its response with other fans.
- Test the network wiring to fan 3 for opens or shorts using the manufacturer's procedure.
- If power, ground, and network wiring pass, follow the manufacturer's diagnostic steps to confirm a failed fan 3 controller or assembly.
Common fixes
- Reconnect fan 3 and repair damaged connector or harness wiring.
- Replace a failed fuse or repair the fan's power or ground connection after finding the cause.
- Repair an open or short in the network wiring to fan 3.
- Replace the confirmed failed fan 3 controller or fan assembly.
Can I keep driving?
Watch the coolant temperature and avoid idling in traffic, towing, or other high-load driving until fan 3 works; overheating can damage the engine. Pull over and shut the engine off if the temperature rises into the danger range.
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.