P0494
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.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Fan 1 motor worn or brushes degradedCommon
- High contact resistance in feedPossible
- Fan impeller seized or blockedLess likely
Parts involved
- Cooling Fan 1
- Fan Motor 1
- Fan Speed Sensor 1
P0494 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.