What it means
Module cooling fan circuit electrically OK but fan does not run as commanded — bearing seized, blade obstructed, or driver weak.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
The control module cooling fan is meant to circulate air when the module needs extra cooling. U350F is set when the circuit appears electrically usable but the fan does not respond as expected to a command, such as when the motor is seized or airflow is obstructed.
Common causes
Most likely first.
- Fan motor seized
- 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
- Check freeze-frame data and scan for fan, temperature, and communication codes to learn when the fan was expected to operate.
- Inspect the named module fan and its intake and outlet for debris, a blocked blade, physical damage, or a loose connector.
- Command the fan on with a scan tool under the manufacturer's specified conditions and confirm whether it turns freely and responds consistently.
- Check fan supply voltage, ground, and control signal during the command, comparing results with the manufacturer's specification.
- If the circuit signals are correct but the fan does not respond, check for a seized motor or weak module driver using vehicle-specific procedures.
Common fixes
- Remove debris or an obstruction from the fan and its airflow path.
- Reconnect or repair loose or damaged fan wiring.
- Replace a fan motor that is seized or fails to run when commanded.
- Repair a confirmed module fan driver fault after verifying the circuit.
Can I keep driving?
If the module temperature rises, a warning appears, or vehicle functions become limited, stop driving when safe because continued heat can cause the module to shut down or be damaged. Otherwise, keep driving limited and monitor for temperature or function warnings.
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.