Failed oxygen sensor heater element inside the HO2S12 sensor, which is the most common cause on higher-mileage Kia engines; Corroded, loose, or pushed-back pins in the oxygen sensor connector or the engine computer connector; Damaged or chafed heater circuit wiring between the sensor and the engine computer, often near the exhaust manifold or underbody; Blown fuse or faulty relay that supplies power to the oxygen sensor heater circuit; High-resistance ground connection for the heater circuit at the engine block or chassis; Engine computer driver circuit fault, which is rare but possible after a shorted heater element; Aftermarket oxygen sensor with incorrect heater resistance that does not match Kia specifications

DTC codes / Kia codes / P1115

P1115 · KiaH02S12 Heater Circuit Low Voltage

Q: What does code P1115 mean?

H02S12 Heater Circuit Low Voltage. P1115 on a Kia means the engine computer has detected low voltage on the heater circuit of the downstream oxygen sensor, identified as HO2S12 (Heated Oxygen Sensor, bank 1 sensor 2). The sensor's internal heater is not drawing the current the computer expects, so the exhaust sensor may stay cold and stop reporting accurate air-fuel data.

P1115 on a Kia means the engine computer has detected low voltage on the heater circuit of the downstream oxygen sensor, identified as HO2S12 (Heated Oxygen Sensor, bank 1 sensor 2). The sensor's internal heater is not drawing the current the computer expects, so the exhaust sensor may stay cold and stop reporting accurate air-fuel data.

SystemPowertrain

Code typeKia specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illuminated check engine light, often with no other symptoms besides the warning light
Slightly higher fuel consumption because the engine computer falls back to a default fuel mixture
Rough or unstable idle when the engine is cold and the sensor heater cannot warm the element
A pending or stored P1115 that returns immediately after clearing if the circuit fault is still present
In rare cases, a slight hesitation or stumble during light acceleration from a stop

Common causes, most likely first

Failed oxygen sensor heater element inside the HO2S12 sensor, which is the most common cause on higher-mileage Kia engines
Corroded, loose, or pushed-back pins in the oxygen sensor connector or the engine computer connector
Damaged or chafed heater circuit wiring between the sensor and the engine computer, often near the exhaust manifold or underbody
Blown fuse or faulty relay that supplies power to the oxygen sensor heater circuit
High-resistance ground connection for the heater circuit at the engine block or chassis
Engine computer driver circuit fault, which is rare but possible after a shorted heater element
Aftermarket oxygen sensor with incorrect heater resistance that does not match Kia specifications

How to diagnose and fix it

Check the fuse and relay that feed the oxygen sensor heater circuit, then confirm battery voltage at the heater supply wire with the key on
Inspect the HO2S12 connector for corrosion, loose pins, or water intrusion and clean or repair as needed
Measure the heater element resistance across the sensor heater terminals and compare it to Kia specifications for that engine
Check the heater ground circuit for excessive resistance using a voltage drop test while the circuit is loaded
Trace the heater wires for chafing or breaks and repair any damaged section with proper solder and heat shrink
If the circuit and fuse are good but the heater resistance is out of range, replace the HO2S12 sensor with an OEM-quality part
Clear the code, run the engine through a cold-start warm-up cycle, and verify the heater monitor passes without P1115 returning

Why the heater circuit fails on Kia

A P1115 can set from a heater element that has partially failed and still shows continuity on a basic ohm test, so compare the measured resistance to the exact Kia specification rather than just checking for an open circuit.
The downstream sensor heater shares power with other emissions components on many Kia models, so a blown fuse that feeds the HO2S12 heater may also disable the evaporative emissions purge circuit and set companion codes.
Technicians often replace the oxygen sensor when the real fault is a corroded ground on the engine block, which raises heater circuit resistance and mimics a failed sensor heater.
An aftermarket oxygen sensor with the wrong heater resistance can set P1115 even though the sensor is new, so verify the part number and resistance against the original Kia sensor.
The engine computer may not command closed-loop fuel control until the downstream heater circuit passes its self-test, so a P1115 can cause a persistent rich or lean fuel trim pattern that looks like a different fault.

Can I keep driving with P1115?

You can usually drive the car with P1115 because the engine computer substitutes a default heater strategy, but avoid long periods of idling and heavy load until the fault is repaired. Prolonged driving with a cold downstream sensor can increase emissions and may eventually damage the catalytic converter.

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.