What Does P1479 Mean?
The high-speed cooling fan control circuit has experienced a malfunction in the primary control path. The PCM has detected an issue with the high fan speed relay circuit, wiring, or control module.
Common Causes
30%
Failed high-speed fan relay
25%
Short or open in fan control circuit wiring
20%
Corroded relay socket or poor connection
15%
Failed fan control module or driver circuit
10%
PCM internal driver circuit failure
Diagnostic Steps
1
Step 1: Locate and test high-speed fan relay, swap with known good relay to verify operation
2
Step 2: Command high-speed fan operation using scan tool and monitor for response
3
Step 3: Check relay socket for corrosion, damage, or loose pins
4
Step 4: Test voltage and ground at relay socket with ignition on
5
Step 5: Use multimeter to test control signal from PCM/fan module to relay coil during commanded operation
Estimated Repair Cost
$150 - $500
Parts + labor, varies by vehicle and location
The high-speed cooling fan control circuit has experienced a malfunction in the primary control path. The PCM has detected an issue with the high fan speed relay circuit, wiring, or control module.
The most common cause of P1479 (High Fan Control Primary Circuit Malfunction) is: Failed high-speed fan relay
Typical repair costs for P1479 range from $150 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Moderate concern as high-speed fan may not engage during high cooling demand. Risk of overheating in extreme conditions, heavy loads, or trailer towing.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1479 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Cooling System
Difficulty
Type
Manufacturer
Recommended Tools
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