P0720 on Kia: How to Diagnose & Fix
Output Speed Sensor Circuit Malfunction
1 Kia model · 1 documented issue · 1 critical · $250-$2,800 repair
P0720 on Kia by model: symptoms, diagnosis and fix
Complaints show a recurring pattern of automatic transmission malfunction on early Optimas, including hesitation, refusal to go into gear, harsh downshifts, and limp-home operation. Several reports specifically mention input and output speed sensor failure causing the transmission to drop from 4th gear and shift only between lower gears.
Common Symptoms
- Transmission drops from 4th to 3rd gear
- Vehicle will not go into gear
- Harsh or delayed shifting
- Only shifts between 2nd and 3rd in manual/sport mode
- Hesitation on acceleration
How to Fix
Scan the transmission control system and verify operation of the input and output speed sensors, transmission range inputs, and fluid condition. Repairs often involve replacing one or both speed sensors and servicing the transmission fluid; if internal damage has occurred from prolonged operation, rebuild or replacement can push costs much higher, from about $250 to $2,800.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Kia 42620-39051 automatic-transmission input speed sensorOEMKia 42620-39051
Replace an input/turbine-speed sensor with a confirmed signal or circuit failure Fitment/availability: 2001-2002 Kia Optima four-speed automatic, 2.4L or 2.5L; confirm VIN, transmission ID, connector and current supersession before purch…
- Genuine Kia 42621-39052 automatic-transmission output speed sensorOEMKia 42621-39052
Replace an output-speed sensor with a confirmed signal or circuit failure Fitment/availability: 2001-2002 Kia Optima four-speed automatic, 2.4L or 2.5L; confirm VIN, transmission ID, connector and current supersession before purchase.
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Owner tips & cautions
- TipIf the transmission suddenly starts downshifting or gets stuck in lower gears, scan it immediately before continued driving damages the unit.
P0720 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0720 mean on a Kia?
P0720 stands for "Output Speed Sensor Circuit Malfunction." P0720 indicates a malfunction in the transmission output speed sensor circuit. The output speed sensor measures how fast the transmission's output shaft is turning, which the computer uses to calculate vehicle speed, control shift timing, and manage torque converter lockup. When the signal is missing or implausible, the transmission may shift harshly, get stuck in one gear (limp mode), or the speedometer may read incorrectly. The fault is usually in the sensor, its wiring, or the connector, though internal transmission issues can also be responsible. On Kia it is documented across 1 model: Optima.
What are the most common causes of P0720?
The most common causes of P0720 are: Failed output (vehicle) speed sensor, Damaged wiring, connector, or corrosion in the sensor circuit, Metal debris on the sensor tip or damaged reluctor ring, Open or short in the signal circuit, Low or contaminated transmission fluid affecting components, Poor ground or reference voltage to the sensor, Faulty transmission control module (TCM/PCM). The specific cause varies by vehicle.
How much does it cost to fix P0720 on a Kia?
Published repair estimates on Kia range from $250 to $2,800 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0720 on a different make?
View P0720 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.