Faulty low speed fan control relay (stuck contacts or failed coil); Damaged, chafed or corroded wiring between the relay and the powertrain control module; Corroded or loose connector at the relay, fuse box or powertrain control module; Blown fuse or poor power or earth supply to the relay circuit; Failed fan motor or its wiring causing a short that affects the relay circuit; Internal fault in the powertrain control module relay driver.

P1490

Low Speed Fan CTRL Relay Circuit Open Or Shorted.

Jeep
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

On Jeep, P1490 means the powertrain control module has detected an open or shorted circuit on the low speed radiator fan control relay. The module monitors the relay driver circuit and sets the code when the voltage it sees does not match what it commanded. Exact relay layout and fan arrangement depend on the model and engine.

Symptoms

Engine temperature gauge rising in traffic or when idling
Radiator fan not running, or running constantly at low speed
Air conditioning performing poorly when stationary
Malfunction indicator lamp on
Engine overheating warning
Fan running after the engine is switched off

Possible causes

Faulty low speed fan control relay (stuck contacts or failed coil)likely
Damaged, chafed or corroded wiring between the relay and the powertrain control modulelikely
Corroded or loose connector at the relay, fuse box or powertrain control modulelikely
Blown fuse or poor power or earth supply to the relay circuitpossible
Failed fan motor or its wiring causing a short that affects the relay circuitpossible
Internal fault in the powertrain control module relay driverrare

How to diagnose

Read the stored and pending codes and note the freeze frame data, including coolant temperature and whether other fan or cooling codes are present
Check the coolant level and condition, and look for obvious cooling system faults, because overheating can mask the true cause
Inspect the relevant fuses and the relay for heat damage, corrosion or water ingress
Visually inspect the wiring and connectors from the relay to the fan and to the powertrain control module for chafing, melting or green corrosion
Using a scan tool bi-directional test, command the low speed fan on and off and listen and watch for a response and a click from the relay
Swap the relay with a known good one of the same type, if the layout allows, and retest
Measure the supply voltage, earth and control signal at the relay socket against the wiring diagram for your model and engine
Check the fan motor current draw and wiring for shorts or high resistance

How to fix

Replace the faulty low speed fan relay
Repair or replace damaged wiring and clean or renew corroded connector terminals
Replace the blown fuse after finding and correcting the cause of the overload
Restore a good power or earth supply to the relay circuit
Replace the fan motor or fan assembly if it is shorting or drawing excess current
Replace or repair the powertrain control module only after all wiring and relay faults are ruled out

Can I keep driving?

Medium severity

Short, careful journeys are possible, but without a working fan the engine can overheat in slow traffic or when stationary. Watch the temperature gauge and stop at once if it climbs; get it repaired soon.

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