Additional Fan Relay Circuit Malfunction (Ford)
What does P1477 mean?
The P1477 code means the vehicle's onboard diagnostic system has detected: Additional Fan Relay Circuit Malfunction (Ford). This is a moderate severity code.
Common Symptoms
- Auxiliary cooling fan does not operate
- Check Engine Light illuminated
- Higher than normal coolant temperatures in traffic
- AC condenser cooling reduced
- Temperature gauge creeps up at idle
Probable Causes (Ranked by Likelihood)
- Failed auxiliary fan relay Very High
- Blown auxiliary fan fuse High
- Faulty auxiliary fan motor Moderate
- Corroded wiring at the auxiliary fan connector Moderate
- PCM relay driver circuit failure Low
Step-by-Step Diagnostic Procedure
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Locate and test the auxiliary fan relay by swapping it with an identical relay in the fuse box.
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Check the auxiliary fan fuse for continuity.
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Apply 12V directly to the auxiliary fan motor to test if it spins.
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Inspect the fan motor connector and wiring for corrosion or damage.
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Command the auxiliary fan with a scan tool and verify the PCM output signal at the relay.
Frequently Asked Questions
What is the additional fan on Ford vehicles?
Some Ford vehicles have a secondary or auxiliary cooling fan in addition to the primary fan. It provides extra cooling during heavy AC use, towing, or high ambient temperatures.
Do all Fords have an auxiliary fan?
No. The auxiliary fan is found primarily on larger vehicles like the Expedition, Explorer, and F-150, and on some models with the tow package or heavy-duty cooling option.
Can I drive without the auxiliary fan?
For normal driving in mild weather, yes. However, during hot weather, towing, or extended idling, the lack of the auxiliary fan can lead to higher coolant temperatures and potential overheating.