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GTECH Calibration
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P1491

Radiator Fan Control Relay Circuit Open Or Shorted.

  • Plymouth
  • Powertrain
  • Manufacturer code
  • High severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
4
AreaAuxiliary emission controls
91
FaultThe specific fault in that area

What it means

On Plymouth models, P1491 means the engine control unit has detected a fault in the radiator fan control relay circuit. It saw an open circuit or a short where the control unit's expected voltage or current feedback for the relay did not match what it commanded. The cooling fan may therefore not run when needed, or may run when it should not.

Symptoms

  • Check engine light on
  • Engine running hotter than normal, especially in traffic or when idling
  • Temperature gauge rising when stationary
  • Cooling fan not running, or running constantly
  • Air conditioning performing poorly at idle or in slow traffic

Possible causes

  • Faulty radiator fan control relay (failed coil or stuck contacts)likely
  • Damaged, chafed or corroded wiring between the relay and the engine control unitlikely
  • Poor connection or corrosion at the relay socket or connector terminalslikely
  • Blown fuse or fault in the relay's power or earth supplypossible
  • Faulty cooling fan motor drawing excessive current or shortingpossible
  • Fault inside the engine control unit's relay driverrare

How to diagnose

  1. Read the stored codes and freeze frame data, noting engine temperature, vehicle speed and whether other cooling or air conditioning codes are present.
  2. Check the engine coolant level and condition when cold, and look for obvious cooling system faults that could be mistaken for a fan fault.
  3. Inspect the relay, fuse and relay socket for heat damage, corrosion, loose terminals or water ingress.
  4. Inspect the wiring and connectors from the relay to the control unit and to the fan for chafing, burns or broken wires.
  5. Command the fan on with a suitable scan tool output test, if supported, and listen for the relay clicking and the fan running.
  6. Test the relay coil and contacts on the bench, or swap in a known good identical relay to see if the fault changes.
  7. Check for correct power and earth at the relay socket and measure the control circuit voltage for an open or short, following the wiring diagram for the specific model and engine.
  8. Check the fan motor current draw and condition if the relay and wiring prove sound.

How to fix

  • Replace the faulty radiator fan control relay with a correct specification part.
  • Repair or replace damaged wiring and connectors in the relay control circuit.
  • Clean or replace corroded relay socket terminals and fix any poor earth connections.
  • Replace the blown fuse after finding and correcting the cause of the overload.
  • Replace the cooling fan motor if it is drawing excessive current or is shorted.
  • Repair or replace the engine control unit only if all wiring, relay and supply checks are good and the driver fault is confirmed.

Can I keep driving?

High severity

Avoid driving until the cooling fan operation is confirmed, as overheating can quickly cause serious engine damage. If you must move the car, make only a short journey, keep a close eye on the temperature gauge and stop at once if it rises.

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

This code for other makes

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