What P0121 Means for Your 2022 Lexus IS
A P0121 code on your 2022 Lexus IS indicates the ECM has detected an inconsistent throttle position sensor signal. The voltage is within normal bounds but doesn't properly correlate with your accelerator pedal input—the digital detective in your IS has flagged a discrepancy that needs resolution.
The 2022 IS comes as the IS 300 (2.0L turbo-four DI for RWD, 3.5L V6 D-4S for AWD) and IS 350 (3.5L V6 with D-4S dual injection). The IS 500 uses a 5.0L V8 (2UR-GSE) with D-4S. All models feature electronic throttle control with integrated TPS. The D-4S system's port injection component helps keep throttle bodies cleaner.
Symptoms to Expect
- Check engine light on
- Hesitation during acceleration
- Idle quality below Lexus standards
- Throttle response inconsistency
- Possible brief power loss under load
Most Common Causes
- Carbon deposits on throttle body – PCV vapor carbon accumulation on the throttle plate. More common on the 2.0L turbo DI IS 300 than V6 models with D-4S. Likelihood: 40%
- Throttle body motor or sensor wear – Internal component degradation within the electronic throttle body. Likelihood: 25%
- Connector or wiring corrosion – Engine bay heat and age affecting the throttle body connector. Likelihood: 15%
- ECM software update – Toyota/Lexus calibration update for throttle mapping. Likelihood: 10%
- Air intake system leak – Cracked intake boot or loose turbo connection (2.0T). Likelihood: 10%
Repair Cost Estimates
- Throttle body cleaning: $100–$180 (shop) / $10–$25 (DIY)
- Throttle body replacement: $350–$650 parts and labor
- Wiring repair: $100–$250
- ECM update: $100–$200 (dealer)
Check Your Warranty
Your 2022 IS may still be within Lexus's 4-year/50,000-mile basic warranty depending on purchase date and mileage. If covered, have the dealer handle it at no cost. If out of warranty, throttle body cleaning is moderate difficulty. After cleaning, reset the throttle adaptation by disconnecting the battery for 30 minutes, then idling for 10–15 minutes without touching the gas pedal.
How AutoDetective AI Can Help
Upload your OBD-II scan data to AutoDetective for an AI diagnosis that accounts for your IS's specific engine variant (2.0T, 3.5L V6, or 5.0L V8) and mileage. Get a prioritized cause list and local cost estimates.