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OBD-II Code

P0484

Severity

Not yet reviewed

Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.

Can you drive it

We cannot say

Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.

Indicative cost (USD)

$120–$900

From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.

$120 (relay or ground strap) to $900 (full fan assembly + module on a BMW N55).

P0484 is a cooling-fan rationality fault — the ECM/BCM commanded the fan to a specific speed or state and the feedback signal (PWM duty cycle, current draw, or speed sensor input on smart fans) did not match the commanded value within the manufacturer's allowed window.

How a shop works this

Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.

  1. Note every code that is set, not just this one.

    Codes that appear together usually narrow the cause faster than any one of them read alone.

  2. Read the freeze frame — the conditions the fault was recorded under.

    Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.

  3. Confirm the fault is current rather than history.

    Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.

  4. Then follow the diagnostic notes further down this page, in the order they are written.

    They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.

If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.

Common symptoms

  • Check engine light
Read the full diagnostic procedureP0484 is a cooling-fan rationality fault — the ECM/BCM commanded the fan to a specific speed or state and the feedback signal (PWM duty cycle, curren…

P0484 is a cooling-fan rationality fault — the ECM/BCM commanded the fan to a specific speed or state and the feedback signal (PWM duty cycle, current draw, or speed sensor input on smart fans) did not match the commanded value within the manufacturer's allowed window. This is different from P0480/P0481/P0482 (specific relay or speed-control circuit faults); P0484 is the "you asked for X, you got Y" code. On modern PWM fans, normal commanded duty cycle sweeps from 0% (off) to 100% (max) and the current draw sits at 3-8A at low speed, 15-30A at full duty, with brief inrush spikes of 40-60A on startup.

Cheapest-first ladder

  1. scan-tool live data for commanded fan duty vs actual fan speed (or actual current draw on amperage-feedback systems).
  2. At idle with AC off, expect 0-20% commanded; with AC on or coolant past ~210F, expect 30-60%; at high load or coolant past ~225F, expect 70-100%. If commanded jumps but actual stays flat, the fan or driver is the suspect.
  3. Backprobe the fan power feed with a clamp meter during a duty-cycle sweep — current should track duty linearly within +/- 10%. Then check the fan ground (drop test, less than 0.2V under load) and the PWM signal at the fan connector with a scope (clean square wave, no chattering edges).
  4. Expensive-misdiagnosis caveat: a $40 cracked solder joint inside the fan-control module (FCM) or a single bad ground strap will exactly mimic a $300-$700 failed fan motor — always verify the control side before replacing the fan assembly.
Vehicle-specific patterns1997-2014 Ford F-150 (4.6L, 5.4L, 6.2L, 3.5L EcoBoost) uses a PWM electric fan with a dedicated Fan Control Module bolted to the shroud and is the mo…
  • 1997-2014Ford F-150 (4.6L, 5.4L, 6.2L, 3.5L EcoBoost) uses a PWM electric fan with a dedicated Fan Control Module bolted to the shroud and is the most common P0484 case in domestic shops — the FCM cracks internally from heat cycles and either commands the fan to max constantly or fails to respond at all.
  • 2007-2014GM 1500/2500 trucks (Silverado, Sierra, Tahoe, Yukon) use BCM-controlled dual electric fans and frequently throw P0484 when the BCM's fan driver MOSFETs degrade — the symptom is fan running constantly with AC off, or never spinning up under load.
  • 2008-2020Dodge Grand Caravan / Chrysler Town & Country with the 3.3L / 3.8L / 3.6L V6 uses a hybrid setup (mechanical clutch fan plus auxiliary electric) and throws P0484 when the auxiliary fan relay corrodes in the underhood TIPM (Totally Integrated Power Module) — Chrysler issued multiple TSBs on TIPM failures.
  • 2010-2016BMW with the N20/N55 platform (328i, X3, X5 35i) throws P0484 when the electric fan module fails internally; common in 80k-120k mile range.

Estimated repair$120 (relay or ground strap) to $900 (full fan assembly + module on a BMW N55).

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