What Does P0121 Mean on a 2024 Kia Forte?
P0121 on your 2024 Kia Forte means the throttle position sensor (TPS) is communicating within the expected voltage range but with an abnormal performance pattern. Our diagnostic investigation found that the ECM detects TPS readings that don't match its calculations from pedal input, airflow, and engine load.
The 2024 Forte runs the 2.0L MPI four-cylinder (147 hp) with a CVT. The MPI (Multi-Point Injection/port injection) fuel system helps keep the throttle body and intake valves clean—a real advantage for throttle body health. The TPS is integrated into the electronic throttle body assembly.
Common Symptoms to Watch For
- Check engine light on
- Hesitation during acceleration from stops
- Rough or unstable idle
- CVT feels sluggish or jerky
- Reduced throttle response during passing
- Decreased fuel economy
Top Causes Ranked by Likelihood
- ECM software calibration (35%) – Current-year vehicles benefit from ongoing calibration refinements. Cost: $0 under warranty.
- Throttle body manufacturing defect (30%) – Factory defect in the throttle body or TPS element. Cost: $0 under warranty.
- Wiring or connector defect (20%) – Assembly variability in harness or connector. Cost: $0 under warranty.
- Carbon buildup (10%) – Unlikely at low mileage; MPI further reduces risk. Cost: $100–$225 if not covered.
- Intake system leak (5%) – Factory clamp or gasket issue. Cost: $0 under warranty.
How Serious Is This Code?
P0121 is medium severity. The Forte's 2.0L has modest power reserves—any throttle hesitation is very noticeable. Schedule a dealer visit soon.
Diagnostic Path
Take your 2024 Forte to a Kia dealer. KDS (Kia Diagnostic System) diagnostics and any repairs are covered under warranty.
Can You Fix This Yourself?
Kia's warranty matches Hyundai's: 5yr/60k basic + 10yr/100k powertrain (original owner). Everything is covered—go to the dealer.
Get a Free AI Diagnosis
Know what to expect before your appointment. AutoDetective's free AI diagnosis provides a targeted preliminary analysis of your Forte's P0121.