Faulty fuel injector number 1 (internal coil short or open); Damaged or corroded electrical connector at the injector; Chafed, broken, or shorted wire in the injector control circuit; Poor connection or corrosion at the ECM harness connector; Failed ECM driver for the injector circuit (rare but possible); Aftermarket or incorrect injector installed previously

DTC codes / Kia codes / P1225

P1225 · KiaFuel Injector 1 Circuit Low Voltage

Q: What does code P1225 mean?

Fuel Injector 1 Circuit Low Voltage. P1225 on a Kia indicates that the engine control module (ECM) has detected an abnormally low voltage on the control circuit for fuel injector number 1. This means the ECM is commanding the injector to open, but the electrical feedback on that circuit is below the expected threshold, which can prevent the injector from firing correctly and cause a misfire or rough running condition.

P1225 on a Kia indicates that the engine control module (ECM) has detected an abnormally low voltage on the control circuit for fuel injector number 1. This means the ECM is commanding the injector to open, but the electrical feedback on that circuit is below the expected threshold, which can prevent the injector from firing correctly and cause a misfire or rough running condition.

SystemPowertrain

Code typeKia specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or shaking, especially when the engine is cold
Engine misfire or stumble during acceleration
Reduced engine power and poor fuel economy
Difficulty starting or stalling shortly after start-up
A strong fuel odor from the exhaust if the injector is stuck open or leaking

Common causes, most likely first

Faulty fuel injector number 1 (internal coil short or open)
Damaged or corroded electrical connector at the injector
Chafed, broken, or shorted wire in the injector control circuit
Poor connection or corrosion at the ECM harness connector
Failed ECM driver for the injector circuit (rare but possible)
Aftermarket or incorrect injector installed previously

How to diagnose and fix it

Perform a visual inspection of the injector 1 connector and wiring for damage or corrosion
Measure the resistance of fuel injector 1 and compare to the factory specification
Check for battery voltage at the injector connector with the key on and engine off
Use a noid light or oscilloscope to verify the injector pulse signal from the ECM
Inspect the ECM harness connector for loose terminals or corrosion, and repair as needed
If the injector tests bad, replace it with a known-good unit and clear the code
If the circuit and injector are good, diagnose the ECM driver circuit or replace the ECM as a last resort

Don't replace the injector before checking this

A low voltage code on an injector circuit often results from a poor ground connection at the engine block or chassis, not the injector itself.
Kia injectors can fail intermittently when hot, so a resistance test performed on a cold engine may not reveal the fault.
The ECM may set P1225 if the injector circuit is shorted to ground or if the injector coil is partially open, so a simple resistance check is not always conclusive.
Aftermarket injectors with incorrect resistance values can trigger this code even when they appear to function normally.
A misfire from a bad spark plug or ignition coil can sometimes cause the ECM to misinterpret injector feedback and set a false P1225, so always check secondary ignition components first.

Can I keep driving with P1225?

You can drive the vehicle short distances to a repair shop, but avoid heavy acceleration or towing because a misfiring injector can overheat the catalytic converter. If the engine is running very rough or stalling, stop driving and have it towed to prevent further damage.

Tools that help

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