Faulty idle air control solenoid with an internally shorted or open winding on the signal 3 circuit; Damaged or corroded wiring harness between the IAC solenoid and the ECM, including chafed insulation or broken strands; Poor electrical connection at the IAC solenoid connector or the ECM connector, such as loose pins or corrosion; Carbon buildup or mechanical binding inside the IAC valve, causing the solenoid to draw abnormal current and set a low-input code; Failed ECM driver circuit for the IAC solenoid signal 3 channel, though this is less common than wiring or solenoid faults; Aftermarket or incorrect IAC solenoid installed previously that does not match the Subaru resistance specification

DTC codes / Subaru codes / P1514

P1514 · SubaruIdle Air Control Solenoid Signal 3 Circuit Low Input

Q: What does code P1514 mean?

Idle Air Control Solenoid Signal 3 Circuit Low Input. P1514 on a Subaru means the engine control module (ECM) has detected a low-voltage condition on the signal circuit for the idle air control (IAC) solenoid, specifically on signal channel 3. The ECM expects to see a voltage within a normal range on that circuit, and a reading below the threshold indicates a short to ground, an open circuit, or a faulty solenoid winding.

P1514 on a Subaru means the engine control module (ECM) has detected a low-voltage condition on the signal circuit for the idle air control (IAC) solenoid, specifically on signal channel 3. The ECM expects to see a voltage within a normal range on that circuit, and a reading below the threshold indicates a short to ground, an open circuit, or a faulty solenoid winding.

SystemPowertrain

Code typeSubaru specific

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Unstable or fluctuating idle speed, sometimes surging or dipping below normal
Engine stalls when coming to a stop or when the throttle is released
Rough idle quality, especially when the engine is cold or under electrical load
Occasional hard starting or the need to hold the throttle open to keep the engine running

Common causes, most likely first

Faulty idle air control solenoid with an internally shorted or open winding on the signal 3 circuit
Damaged or corroded wiring harness between the IAC solenoid and the ECM, including chafed insulation or broken strands
Poor electrical connection at the IAC solenoid connector or the ECM connector, such as loose pins or corrosion
Carbon buildup or mechanical binding inside the IAC valve, causing the solenoid to draw abnormal current and set a low-input code
Failed ECM driver circuit for the IAC solenoid signal 3 channel, though this is less common than wiring or solenoid faults
Aftermarket or incorrect IAC solenoid installed previously that does not match the Subaru resistance specification

How to diagnose and fix it

Verify the code with a scan tool and check for any related idle control or misfire codes before beginning diagnosis
Inspect the IAC solenoid connector and the ECM connector for corrosion, loose pins, or pushed-back terminals, and repair as needed
Measure the resistance of the IAC solenoid winding on the signal 3 circuit and compare it to the Subaru service specification for the vehicle
Check the signal 3 circuit for a short to ground or an open circuit using a digital multimeter and a wiring diagram, repairing any damaged wire
Clean the IAC valve passages and throttle body of carbon deposits if mechanical binding is suspected, then recheck the code
If the solenoid fails the resistance or functional test, replace the idle air control solenoid with a correct Subaru-specified part
Clear the code and perform an idle relearn or drive cycle as required by the Subaru service procedure, then confirm the code does not return

What a low IAC signal really means

A low-input code on the IAC signal circuit often results from a short to ground in the harness rather than a failed solenoid, so always inspect the wiring before condemning the valve.
Carbon buildup inside the IAC valve can increase solenoid current draw and trigger a low-input code even when the solenoid winding itself tests good.
The ECM driver for the IAC signal 3 circuit can be damaged by a shorted solenoid or a wiring short, so repairing the root cause before replacing the ECM is essential.
Some Subaru models use a stepper-motor IAC valve where signal 3 is one of several coil circuits, and a fault in that one channel can cause idle problems that seem intermittent.
A poor ground connection at the engine or chassis can create a voltage drop that mimics a low signal on the IAC circuit, so ground integrity should be part of the diagnostic routine.

Can I keep driving with P1514?

You can usually drive the vehicle to a repair shop, but expect an unstable idle and possible stalling when you come to a stop. Avoid heavy electrical loads and prolonged idling until the fault is repaired, and do not continue driving if the engine stalls repeatedly in traffic.

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.