Fan 1 Underspeed
Cooling fan 1 is rotating slower than commanded. The ECU sees the tachometer feedback below the expected window for the requested duty cycle - usually a worn fan motor, a high-resistance harness or feed, or a partially seized impeller.
Affected components
- Cooling fan 1
- Fan motor 1
- Fan speed sensor 1
Common causes
- High likelihood: Fan 1 motor worn or brushes degraded
- Medium likelihood: High contact resistance in feed
- Low likelihood: Fan impeller seized or blocked
Diagnostic notes
- The malfunction indicator lamp may illuminate
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.