Faulty low speed fan control relay (internal open or shorted coil); Damaged, chafed or corroded wiring in the relay control circuit (open circuit or short to ground or voltage); Corroded, loose or burnt relay socket or connector terminals; Blown fuse or missing power supply to the relay; Fault in the fan motor or its wiring that loads the relay circuit; Faulty engine control unit driver circuit.

P1490

Low Speed Fan CTRL Relay Circuit Open Or Shorted.

Plymouth
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
4: AreaAuxiliary emission controls
90: FaultThe specific fault in that area

What it means

P1490 on a Plymouth means the engine control unit has detected a fault in the circuit that switches the low speed radiator fan control relay. The module commands the relay on or off and monitors the circuit, and it saw a voltage that did not match the command, pointing to an open circuit or a short. The fault is in the relay control circuit, not necessarily a failed fan motor.

Symptoms

Check engine light on
Radiator fan not running at low speed or not running at all
Engine temperature climbing in traffic or when idling
Air conditioning performing poorly at idle or in slow traffic
Fan running constantly or at the wrong time

Possible causes

Faulty low speed fan control relay (internal open or shorted coil)likely
Damaged, chafed or corroded wiring in the relay control circuit (open circuit or short to ground or voltage)likely
Corroded, loose or burnt relay socket or connector terminalslikely
Blown fuse or missing power supply to the relaypossible
Fault in the fan motor or its wiring that loads the relay circuitpossible
Faulty engine control unit driver circuitrare

How to diagnose

Read the stored codes and freeze frame data, noting engine temperature and speed when the code set, and check for any other cooling or electrical codes
Inspect the relay, fuse, relay socket and connectors for heat damage, corrosion, loose terminals and water ingress
Check the coolant level and look for obvious cooling system problems that could be mistaken for a fan fault
Command the fan on with a suitable scan tool output test, if the model supports it, and listen for the relay clicking and the fan running
Test the relay itself: coil resistance and contact operation, or swap with a known good identical relay
Check the relay power supply and fuse with a multimeter, and check earth connections
With the relay removed, test the control wire from the engine control unit to the relay for continuity, short to ground and short to voltage, using the wiring diagram for that model and engine
If wiring and relay are sound, check the fan motor current draw and then consider the engine control unit driver

How to fix

Replace the faulty low speed fan relay with the correct specification part
Repair or replace damaged wiring in the relay control circuit, ensuring it is properly secured and protected
Clean or replace corroded or damaged relay socket terminals and connectors
Replace the blown fuse after finding and correcting the cause of the overload
Repair or replace the fan motor if it is drawing excessive current or is seized
Replace or repair the engine control unit only after all wiring, relay and power supply faults are ruled out

Can I keep driving?

Medium severity

The car can be driven short distances if the temperature gauge stays normal, but without a working low speed fan it may overheat in traffic or at idle. Get it fixed soon and stop if the temperature rises to avoid engine damage.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.