What Does P0121 Mean on a 2024 Acura MDX?
A P0121 on your 2024 Acura MDX tells the ECM that the throttle position sensor signal is within voltage range but exhibiting an irregular pattern. The digital detective in your MDX has flagged a communication issue between the throttle body and the engine computer that warrants closer inspection.
The 2024 MDX continues with the 3.5L V6 (J35Y6) with port fuel injection as standard, and the Type S variant carries the 3.0L twin-turbo V6 with direct injection. Both use Honda's electronic throttle control system with integrated TPS. On a vehicle this new, P0121 typically points to software or manufacturing quality rather than wear.
Symptoms
- Check engine light on
- Subtle hesitation during acceleration
- Idle smoothness slightly degraded
- Throttle response may feel inconsistent
- Possible brief power delivery irregularity
Top Causes on a New MDX
- ECM software calibration – Honda/Acura regularly refines throttle mapping and powertrain software. This is the most likely cause on a new vehicle. Likelihood: 35%
- Carbon deposits – Short-trip driving can produce throttle body deposits quickly, especially on the Type S's DI engine. Likelihood: 25%
- Throttle body manufacturing defect – Occasional quality issue with the TPS or motor assembly. Likelihood: 25%
- Connector or wiring issue – Factory assembly connection problem. Likelihood: 10%
- Intake system leak – Loose boost piping (Type S) or intake duct. Likelihood: 5%
Cost to Fix
- All repairs: $0 under warranty
- Out-of-warranty reference: Cleaning $100–$180, replacement $350–$600, software $100–$200
Head to the Acura Dealer
Your 2024 MDX is fully covered under Acura's 4-year/50,000-mile basic warranty and 6-year/70,000-mile powertrain warranty. Do not attempt DIY—take it to your Acura dealer for a no-cost repair. The dealer will use Honda Diagnostic System (HDS) to analyze the throttle body data, apply any software updates, and replace hardware if needed.
How AutoDetective AI Can Help
AutoDetective's AI can analyze your 2024 MDX's scan data to determine whether you have a simple software issue or a hardware problem. Upload your data for a free preliminary diagnosis before the dealer visit.