What Does P0121 Mean on a 2021 Hyundai Palisade?
When P0121 appears on your 2021 Hyundai Palisade, our diagnostic investigation traces the evidence to the throttle position sensor (TPS). The sensor is transmitting within the normal voltage range but with a pattern the ECM considers abnormal—the data doesn't match calculations from pedal input, airflow, and engine load.
The 2021 Palisade—Hyundai's flagship three-row SUV—is powered by the 3.8L Lambda II V6 (291 hp) with an 8-speed automatic. This V6 uses multi-point injection (MPI/port injection), which is excellent for throttle body and intake valve cleanliness. The TPS is integrated into the electronic throttle body.
Common Symptoms to Watch For
- Check engine light on
- Hesitation during acceleration, especially loaded
- Rough or fluctuating idle
- 8-speed automatic may shift at unexpected points
- HTRAC AWD may not distribute torque smoothly
- Smart Cruise Control may disengage
Top Causes Ranked by Likelihood
- Carbon buildup on throttle body (30%) – Even with port injection, PCV gases deposit carbon over time. At 3-5 years, early buildup is possible. Cost: $150–$300.
- Throttle body assembly failure (25%) – Internal TPS defect or early wear. Cost: $0 under warranty; $300–$530 otherwise.
- ECM software calibration (25%) – An available update may refine throttle monitoring. Cost: $0 under warranty.
- Wiring or connector issue (15%) – Corrosion or assembly variability. Cost: $0 under warranty; $80–$250 otherwise.
- Intake system leak (5%) – A gasket or vacuum issue. Cost: $0 under warranty; $100–$300 otherwise.
How Serious Is This Code?
P0121 is medium severity. The Palisade carries up to 8 passengers—reliable power delivery is essential for safe family transport. Fix this soon.
Diagnostic Path
Your 2021 Palisade is under Hyundai's warranty. Take it to the dealer for GDS diagnostics at no cost. The Lambda II V6's throttle body is accessible but dealer diagnosis is most efficient.
Can You Fix This Yourself?
Hyundai's 5yr/60k basic warranty covers your 2021 Palisade. Original owners also have the 10yr/100k powertrain warranty. Dealer repair is free—use it.
Get a Free AI Diagnosis
Get a clear diagnosis before your dealer visit. AutoDetective's free AI analysis targets the most likely cause for your Palisade's P0121.