What Does P0121 Mean on a 2024 Audi A4?
A P0121 on your 2024 Audi A4 means the ECM has caught the throttle position sensor sending data that doesn't match expected patterns. The voltage is in range, but the signal trace is erratic—like a detective reviewing security logs where the timestamps are valid but the events don't follow a logical sequence. The electronic throttle body needs closer inspection.
The 2024 A4 is the final year of the B9.5 generation, powered by the 2.0L TFSI turbocharged four-cylinder (EA888 Gen 3B) producing 201 hp with standard Quattro AWD and a 7-speed S tronic. The EA888's direct injection system is well-documented for carbon accumulation, though on a vehicle this new, software calibration is a leading suspect.
Symptoms to Watch For
- Check engine light and possibly the EPC (Electronic Power Control) warning light
- Hesitation or stumble during acceleration
- Rough or unstable idle
- Turbo boost may feel delayed
- Possible limp mode with limited RPM
Top Causes
- ECM software calibration – As the final model year of this generation, Audi may have pending software updates for throttle mapping. Likelihood: 35%
- Carbon buildup on throttle body – The EA888 DI engine can accumulate deposits even at low mileage with city driving. Likelihood: 30%
- Throttle body assembly defect – Manufacturing quality issue with the TPS or motor. Likelihood: 20%
- Wiring or connector issue – Loose connector or factory routing problem. Likelihood: 10%
- Diverter valve or boost leak – Pressure anomaly at the throttle body. Likelihood: 5%
Repair Costs
- All repairs: $0 under warranty
- Out-of-warranty reference: Cleaning $100–$200, replacement $400–$700, software $100–$250
Warranty Covers This
Your 2024 A4 is fully covered under Audi's 4-year/50,000-mile bumper-to-bumper warranty. Take it to your Audi dealer for no-cost diagnosis and repair. The dealer will use ODIS to run throttle body adaptation, check for software updates, and replace hardware if needed. Do not attempt DIY—warranty coverage makes the dealer the clear choice.
How AutoDetective AI Can Help
Upload your scan data to AutoDetective before your dealer visit. Our AI cross-references EA888-specific patterns and Audi TSBs to preview the likely diagnosis.