Low Speed Fan Relay Circuit Malfunction (Chrysler)
What does P1490 mean?
The P1490 code means the vehicle's onboard diagnostic system has detected: Low Speed Fan Relay Circuit Malfunction (Chrysler). This is a moderate severity code.
Common Symptoms
- Cooling fan does not run on low speed
- Check Engine Light illuminated
- Engine temperature higher than normal in traffic
- Fan only operates at high speed
- AC efficiency reduced at idle
Probable Causes (Ranked by Likelihood)
- Failed low-speed fan relay Very High
- Blown low-speed fan fuse High
- Corroded relay socket terminals Moderate
- Wiring fault in the low-speed circuit Moderate
- PCM relay driver failure Low
Step-by-Step Diagnostic Procedure
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Locate the low-speed fan relay and swap it with an identical relay to test.
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Check the low-speed fan fuse for continuity.
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Inspect the relay socket for burnt or corroded terminals.
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Measure the PCM control signal at the relay when low-speed fan is commanded.
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Test the wiring between the relay, fan motor, and PCM for continuity.
Frequently Asked Questions
Why do I have low speed and high speed fan circuits?
Multiple fan speeds allow the PCM to optimize cooling. Low speed provides adequate cooling at moderate temperatures while minimizing noise and electrical load. High speed is reserved for heavy cooling demands.
Can a relay swap diagnose this problem?
Yes. Many fuse boxes contain multiple identical relays. Swapping the suspected relay with a known good one of the same type is a quick and free way to test if the relay is at fault.
Will the engine overheat without low-speed fan?
Not necessarily. The high-speed fan should still engage at higher temperatures. However, the engine may run warmer than intended in moderate conditions, and the fan will be louder when it does engage.