P0484 — Cooling Fan Rationality Check Malfunction
Drive with caution — fix soon.
What P0484 means
This code sets when the engine computer runs a logic check on the cooling fan and the results don't add up, such as the fan current or operation not matching the commanded state. It often points to a failing fan motor, a stuck relay, or wiring problems. It's commonly fixable with relay, wiring, or fan replacement and rarely involves deeper engine repair.
Common symptoms
- Check engine light is on
- Cooling fan runs constantly or not at all
- Engine temperature higher than usual in traffic
- Air conditioning performance drops at idle
- Occasional blown fan fuse
Common causes
- Failing cooling fan motor
- Stuck or faulty fan relay
- Damaged wiring or poor connections in the fan circuit
- Faulty fan control module
- Coolant temperature sensor sending bad data
Typical repair cost
$130 – $500
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0484 code?
Usually yes for short trips, but watch your temperature gauge closely. Since this code involves how the fan is behaving, overheating is the main risk, especially in slow traffic. If it runs hot, stop and let it cool before continuing.
How much does it cost to fix a P0484 code?
Repairs typically range from $130 to $500. A relay or sensor fix is cheaper, while a full fan motor assembly replacement is at the higher end. Getting an accurate diagnosis first prevents replacing parts you don't need.
Is a P0484 code serious?
It's moderately serious. The car will still run, but a cooling fan that misbehaves can let the engine overheat or repeatedly blow fuses. Address it soon to avoid heat-related engine damage.
What does a rationality check mean for P0484?
It means the computer compared the fan's actual behavior against what it commanded and found a mismatch, like too much current or unexpected operation. It's a logic test rather than a single broken wire, so a proper scan helps pinpoint the exact cause.