P0121 on Your 2022 Lexus RX: What the ECM Detected
A P0121 code on your 2022 Lexus RX means the ECM has flagged an inconsistency in the throttle position sensor signal. The voltage is within normal range, but the pattern doesn't match expected behavior—our detective has found a clue that warrants further investigation of the throttle system.
The 2022 RX is the final year of the fourth-generation (AL20) platform, available as the RX 350 with a 3.5L V6 (2GR-FKS) using both port and direct injection (D-4S), or the RX 450h hybrid. Toyota/Lexus's D-4S system uses port injection to keep intake valves and the throttle body cleaner than DI-only systems, making P0121 less common but not impossible.
Symptoms to Observe
- Check engine light illuminated
- Slight hesitation during acceleration
- Idle may feel rougher than Lexus standards
- Subtle throttle response lag
- Possible reduction in power delivery smoothness
Likely Causes
- Carbon deposits on throttle body – Even with D-4S dual injection, some carbon accumulates over time from PCV vapors. The 2022 model has had enough service life for deposits to form. Likelihood: 40%
- Throttle body motor or sensor wear – The integrated electronic throttle body can develop internal component degradation. Likelihood: 25%
- Wiring or connector issue – Corrosion or looseness at the throttle body connector. Likelihood: 15%
- ECM software update – Toyota/Lexus periodically releases recalibrations for throttle control parameters. Likelihood: 10%
- Air induction system leak – Cracked intake hose or loose clamp after the air filter box. Likelihood: 10%
Estimated Repair Costs
- Throttle body cleaning: $100–$180 (shop) / $10–$25 (DIY)
- Throttle body replacement: $350–$600 parts and labor
- Wiring repair: $100–$250
- ECM update: $100–$200 (dealer)
Warranty & DIY
Your 2022 RX may still be within Lexus's 4-year/50,000-mile basic warranty depending on purchase date and mileage. Check your warranty status first. If out of warranty, throttle body cleaning is a moderate DIY task. Lexus vehicles require a throttle body relearn after cleaning—this can be done through Techstream at a dealer, or by disconnecting the battery for 30 minutes, reconnecting, and idling for 10–15 minutes in Park without touching the accelerator.
How AutoDetective AI Can Help
AutoDetective's AI analyzes your 2022 RX's specific powertrain (V6 or hybrid) and mileage to pinpoint the most likely cause. Upload your scan data for a free, personalized diagnosis.