High Speed Radiator Fan Relay Circuit Malfunction (Chrysler)
What does P1491 mean?
The P1491 code means the vehicle's onboard diagnostic system has detected: High Speed Radiator Fan Relay Circuit Malfunction (Chrysler). This is a critical severity code.
Common Symptoms
- Cooling fan does not operate at high speed
- Engine overheating in heavy traffic or hot weather
- Check Engine Light illuminated
- AC shuts down at high ambient temperatures
- Temperature gauge moves into the red zone
Probable Causes (Ranked by Likelihood)
- Failed high-speed fan relay Very High
- Blown high-speed fan fuse High
- Corroded or melted relay socket High
- Open wiring in the high-speed circuit Moderate
- PCM output driver fault Low
Step-by-Step Diagnostic Procedure
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Check the high-speed fan relay by swapping with an identical relay in the fuse box.
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Inspect the fuse for the high-speed fan circuit.
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Look for burnt or melted terminals in the relay socket.
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Measure voltage at the fan motor high-speed terminal when the relay should be energized.
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Verify the PCM sends a ground signal to the relay coil when high speed is commanded.
Frequently Asked Questions
Is this an emergency repair?
It should be addressed soon. Without the high-speed fan, the engine can overheat quickly in traffic or hot weather. Avoid heavy traffic, towing, and extended idle until repaired.
Why does the relay socket melt?
The high-speed fan draws significant electrical current. If the relay contacts develop high resistance, they generate heat that can melt the plastic socket over time.
Can I wire the fan to run directly as a temporary fix?
You can wire the fan to run continuously through a manual switch, but this increases electrical load and fan noise. It is a temporary measure only until the relay circuit is properly repaired.