Open circuit or broken wire in the relay control circuit between the ECM and cooling fan relay 1; Corroded, backed-out, or damaged terminal at the relay connector or ECM connector; Short to voltage on the control wire, often from chafing against a power feed in the harness; Failed cooling fan relay 1 with an open internal coil or stuck contacts; Faulty ECM driver for the fan relay circuit, though this is uncommon and should be confirmed last; Aftermarket alarm or remote start wiring spliced into the fan circuit causing unintended voltage; Water intrusion into the underhood fuse box or relay block corroding the relay socket

DTC codes / Subaru codes / P1480

P1480 · SubaruCooling Fan Relay 1 Circuit High Input

Q: What does code P1480 mean?

Cooling Fan Relay 1 Circuit High Input. P1480 on a Subaru means the engine control module (ECM) has detected an abnormally high voltage on the control circuit for cooling fan relay 1, which typically indicates an open circuit or a short to voltage rather than a failed relay. The ECM commands the relay to ground to turn the fan on, and when it sees voltage above a calibrated threshold on that command wire, it flags the circuit as high input and may default the fan to continuous operation for safety.

P1480 on a Subaru means the engine control module (ECM) has detected an abnormally high voltage on the control circuit for cooling fan relay 1, which typically indicates an open circuit or a short to voltage rather than a failed relay. The ECM commands the relay to ground to turn the fan on, and when it sees voltage above a calibrated threshold on that command wire, it flags the circuit as high input and may default the fan to continuous operation for safety.

SystemPowertrain

Code typeSubaru specific

SeverityMedium

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light or malfunction indicator lamp (MIL) with no other noticeable symptoms
Cooling fan runs continuously even when the engine is cold or the air conditioning is off
Cooling fan never activates, leading to elevated coolant temperature in traffic or at idle
Engine coolant temperature gauge climbing above normal during prolonged idling
Air conditioning performance degrading because the condenser fan does not engage when requested
In rare cases, a discharged battery if the fan stays powered after the engine is shut off

Common causes, most likely first

Open circuit or broken wire in the relay control circuit between the ECM and cooling fan relay 1
Corroded, backed-out, or damaged terminal at the relay connector or ECM connector
Short to voltage on the control wire, often from chafing against a power feed in the harness
Failed cooling fan relay 1 with an open internal coil or stuck contacts
Faulty ECM driver for the fan relay circuit, though this is uncommon and should be confirmed last
Aftermarket alarm or remote start wiring spliced into the fan circuit causing unintended voltage
Water intrusion into the underhood fuse box or relay block corroding the relay socket

How to diagnose and fix it

Verify the code is current and not a history code by clearing it and test-driving with the scan tool recording freeze-frame data
Inspect cooling fan relay 1, its socket, and the underhood fuse box for corrosion, water intrusion, or loose terminals
Disconnect the relay and measure resistance across its coil; compare to the specified value and replace the relay if open
Backprobe the control wire at the ECM and at the relay with the key on and engine off to check for unexpected voltage
Perform a wiggle test on the harness between the ECM and relay while watching scan tool data to expose an intermittent open
Check for aftermarket accessories spliced into the fan circuit and restore any compromised wiring to factory condition
If the circuit tests good but the ECM never pulls the control wire low, confirm the ECM driver with a known-good relay and then replace the ECM only as a last resort

Why this code often misleads Subaru owners

A P1480 is frequently set by a simple unplugged or loose relay after someone has been working in the underhood fuse box, so always check relay seating before condemning the ECM.
The ECM may command the cooling fan on continuously as a fail-safe when it sees this fault, which can mask the original problem and make the fan appear to work normally.
Subaru fan relay control circuits are ground-side switched, so a short to voltage on the control wire is the usual cause of a high input code rather than a short to ground.
A weak or failing battery can cause the ECM to log this code during cranking if system voltage drops and the relay coil feedback becomes erratic, so check battery health first.
Aftermarket remote starters and alarm systems tapped into the fan relay wiring are a common source of phantom high input codes on older Subaru models.

Can I keep driving with P1480?

You can usually drive a Subaru with P1480 set, but watch the coolant temperature gauge closely and avoid long idles in hot weather or heavy traffic because the fan may not engage when needed. If the temperature gauge climbs above normal or the air conditioning stops cooling, pull over and shut the engine off to prevent overheating damage.

Tools that help

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