What it means
Open circuit at the control module cooling fan (used to keep heavy ECUs like ADAS compute or inverter controllers within thermal limits).
At a glance
- Usually lights the warning light of the system that lost communication
How it works
A control module cooling fan moves air across a high-load module to help keep it within its operating temperature range. The module monitors the fan circuit for continuity; U350C is set when that circuit appears open, so the fan may not be available when cooling is needed.
Common causes
Most likely first.
- Fan motor open
- 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
- Use a scan tool to record freeze-frame data and check for related fan, power, ground, and communication codes before clearing anything.
- Identify the module and fan linked to U350C, then inspect their connectors and wiring for looseness, corrosion, damage, or an unplugged connection.
- With the system in the conditions specified by the manufacturer, command the module cooling fan on and see whether it runs.
- Check the fan's power and ground feeds and test circuit continuity between the fan and module against the manufacturer's specification.
- If the fan and wiring pass, use the vehicle wiring diagram and scan data to check the module output and any gateway or network faults before replacing parts.
Common fixes
- Reconnect a loose fan or module connector and repair damaged wiring.
- Repair an open power or ground connection to the fan.
- Replace the cooling fan motor if its circuit is open.
- Repair a confirmed module output or network routing fault using vehicle-specific service information.
Can I keep driving?
If the affected module is overheating, shutting down, or limiting vehicle functions, stop driving when safe and arrange a repair; continued operation can cause module shutdown or damage. If there are no temperature warnings or operating changes, limit driving and monitor for new 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.