Low Fan Control Primary Circuit Malfunction
Your engine's cooling fan isn't responding properly to the ECU's commands, like a light switch that won't turn on when flipped. This usually means a broken wire, bad relay, or faulty fan motor in the primary cooling circuit.
The ECU monitors the low-speed fan control circuit by checking voltage and current draw through the fan relay and motor. It expects to see proper voltage drop and amperage when commanding the fan on, and detects faults when current falls below minimum threshold or circuit voltage is abnormal.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Fan Motor Current Draw | 3-8 amps when commanded on | Less than 2 amps or open circuit detected |
| Control Circuit Voltage | 12V+ at fan relay coil when active | Below 10.5V or no voltage signal |
Code P1479 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P1479 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.