P0720 on Hyundai: How to Diagnose & Fix
Output Speed Sensor Circuit Malfunction
1 Hyundai model · 1 documented issue · $150-$450 repair
P0720 on Hyundai by model: symptoms, diagnosis and fix
Owners of automatic-transmission Elantras from this generation frequently report sudden harsh shifts, incorrect gear selection, limp mode, or a stuck speedometer caused by failing transmission speed sensors. Hyundai service literature and repair databases commonly reference input and output speed sensor faults on these vehicles. The problem often appears intermittently at first, then becomes more consistent as the sensor signal drops out.
Common Symptoms
- harsh upshifts
- transmission stuck in one gear
- check engine light
- erratic or inoperative speedometer
- delayed shifting
How to Fix
Scan the transmission control system for speed-sensor-related codes and compare live data from the input and output sensors during a road test. Replace the failed sensor(s), inspect the wiring and connector pins for fluid intrusion or corrosion, and verify fluid condition. Clearing codes and performing a drive cycle usually confirms the repair.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Hyundai 42620-39051 automatic-transmission input speed sensorOEMHyundai 42620-39051
Confirm VIN and installed connector bef
- Genuine Hyundai/Kia 42621-39052 automatic-transmission output speed sensorOEMHyundai/Kia 42621-39052
Confirm VIN, transmission and the 42621-39052 number because the part also serves o
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Owner tips & cautions
- TipBefore condemning the transmission, check for speed sensor codes and verify sensor data because many harsh-shift complaints are electrical rather than internal gearbox failure.
- TipIf the transmission fluid is dark or burnt, service it after sensor replacement to improve shift quality and long-term reliability.
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 Hyundai?
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 Hyundai it is documented across 1 model: Elantra.
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 Hyundai?
Published repair estimates on Hyundai range from $150 to $450 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.