What Does P0121 Mean on a 2024 Hyundai Sonata?
A P0121 code on your 2024 Hyundai Sonata sends our investigators to the throttle position sensor (TPS). The sensor is transmitting within the expected voltage range but with an abnormal performance pattern that the ECM flags as inconsistent with other engine data.
The 2024 Sonata—the final model year before Hyundai transitions to the Sonata nameplate's successor—is powered by the 2.5L MPI four-cylinder (191 hp) or the 1.6L Turbo GDI (180 hp) in hybrid form. The MPI engine provides excellent throttle body cleanliness through port injection. The TPS is integrated into the electronic throttle body.
Common Symptoms to Watch For
- Check engine light on
- Hesitation during acceleration
- Rough or unstable idle
- 8-speed automatic or hybrid transmission feels off
- Smart Cruise Control may disengage
- Reduced fuel economy
Top Causes Ranked by Likelihood
- ECM software calibration (35%) – Current-year calibration refinements. Cost: $0 under warranty.
- Throttle body manufacturing defect (30%) – Factory defect in the throttle body or TPS. Cost: $0 under warranty.
- Wiring or connector defect (20%) – Assembly variability. Cost: $0 under warranty.
- Carbon buildup (10%) – Unlikely at low mileage. Cost: $120–$250 if not covered.
- Intake system leak (5%) – Factory issue. Cost: $0 under warranty.
How Serious Is This Code?
P0121 is medium severity. Your Sonata is drivable but may feel sluggish. Warranty covers the fix. Schedule a dealer visit soon.
Diagnostic Path
Dealer visit with GDS diagnostics. Full warranty coverage means free diagnosis and repair.
Can You Fix This Yourself?
Hyundai's 5yr/60k basic warranty + 10yr/100k powertrain warranty covers everything. Take it to the dealer.
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