What it means
A control module has stopped receiving expected network messages from fan 1. The effect on cooling depends on the vehicle's fan and control-system design.
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
Fan 1 is the first cooling fan identified by the vehicle's control system, and its status is communicated to other modules over the network. U0632 sets when expected messages from fan 1 stop arriving; it does not by itself establish whether the fan motor or its communication path is at fault.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module failed
Symptoms
- Warning light or message related to the affected system
- Cooling fan may not operate as intended
How to diagnose it
- Save freeze-frame data and scan all modules for fan, cooling, network, and power-supply codes.
- Check live data for fan 1 status or commanded operation and observe whether the fan responds when the system requests it, following safe test procedures.
- Inspect fan 1's wiring and connectors for damage, corrosion, loose terminals, or heat-related deterioration.
- Verify the fan controller's power and ground against the wiring diagram and manufacturer's specifications.
- Test the network circuit for opens or shorts using the manufacturer's diagnostic procedure, then evaluate the fan 1 controller if wiring and supplies are sound.
Common fixes
- Repair damaged network wiring or loose terminals for fan 1.
- Clean or replace corroded fan 1 controller connectors.
- Restore the fan controller's power or ground connection.
- Replace the fan 1 controller only after network wiring and electrical supplies have been verified.
Can I keep driving?
Avoid driving in heavy traffic, at low speed, or under high engine load if fan 1 may be needed and cooling performance is uncertain. Stop if the temperature rises or a warning appears, because inadequate airflow can overheat the engine, especially while stationary.
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.