01 This Easy Sensor Cleaning Trick Fixes Half of Modern Car Is… • 02 Don’t Ignore These 7 Signs! Your Timing Belt Might Be Faili… • 03 Why Dirty Grounds Cause More Car Problems Than People Reali… • 04 When Should the Oxygen Sensor Be Replaced? A Comprehensive • 05 Unlock the Mysteries of Your Vehicle's Alternator: A Guide … • 06 After 66 Years, Someone Finally Fixed the Seatbelt's Bigges… • 07 Streamlining Fluid Maintenance with RPM Oil Evacuation Syst… • 08 A Comparison of Planetary and Bevel Gears: Types, Functions… • 09 Engine Cranks, Has Spark But Won't Start: Diagnose the Prob… • 10 Charging Anxiety vs. Green Future: Why Americans Aren't Buy… •

DTC codes / GM codes / P1489

P1489 · GMHigh Speed Fan CTRL Relay Circuit Open Or Shorted

P1489 on a GM vehicle means the engine control module (ECM) has detected an open or shorted circuit in the high-speed cooling fan control relay circuit. The ECM commands the relay on or off and monitors the circuit for expected voltage, so this code sets when the feedback does not match the command.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • The check engine light or service vehicle soon light is illuminated.
  • The high-speed cooling fan may run constantly or not at all, depending on whether the circuit is open or shorted.
  • Engine coolant temperature may rise above normal in traffic or during extended idle.
  • The air conditioning may be disabled or blow warm because the ECM inhibits the compressor when fan control is faulty.
  • Often no symptoms besides the warning light, especially if the low-speed fan circuit still functions.

Common causes, most likely first

  1. Failed high-speed fan relay, usually burned contacts or an open coil.
  2. Open or corroded wiring between the ECM and the relay control circuit.
  3. Shorted relay control wire to ground or to battery voltage, often from chafing or heat damage.
  4. Poor ground connection at the relay or fan motor mounting point.
  5. Faulty cooling fan motor drawing excessive current or seized, which can stress the relay circuit.
  6. Damaged or corroded ECM connector pins at the fan control output.
  7. Rarely, an internal ECM driver failure on the fan control circuit.

How to diagnose and fix it

  1. Scan all modules for stored codes and record freeze-frame data to confirm P1489 is current and not history.
  2. Inspect the high-speed fan relay, its socket, and associated fuses for corrosion, burning, or loose terminals.
  3. Test the relay coil and contacts with a multimeter, and swap it with an identical known-good relay to see if the fault follows.
  4. Disconnect the ECM and relay connectors and check for open or shorted wiring with a multimeter, wiggle-testing the harness while watching resistance.
  5. Command the high-speed fan on with a scan tool and verify relay click, voltage at the fan motor, and actual fan operation.
  6. Check the fan motor current draw and ground integrity; replace the motor if it is seized or draws excessive current.
  7. If all external circuits and components test good, diagnose the ECM driver circuit or replace the ECM as a last resort.

What the high-speed fan relay code hides

  • A fan motor that is beginning to seize can intermittently overload the relay circuit and set P1489 without blowing a fuse, so always check motor current draw.
  • The ECM may set this code only after a commanded fan event, so a vehicle that has never been hot enough to trigger high-speed fan operation can carry a pending P1489 without a light.
  • Corrosion inside the underhood fuse box at the relay terminals is a common cause on older GM trucks and SUVs, and it is easy to miss when the relay itself tests good.
  • A shorted fan control wire can back-feed the ECM and cause unrelated drivability codes, so inspect the harness near exhaust manifolds and sharp edges.
  • Replacing the relay without checking the fan motor and ground circuit often leads to a repeat failure because the underlying excessive current draw remains.

Can I keep driving with P1489?

You can usually drive short distances with P1489, but avoid heavy traffic, long idles, and towing until the fan circuit is repaired. If the temperature gauge climbs above normal or the air conditioning stops cooling, pull over and let the engine cool to prevent overheating damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage