What Does P0121 Mean on a 2022 Mercedes-Benz E-Class?
A P0121 code on your 2022 Mercedes-Benz E-Class (W213) tells you the ECU has detected an abnormal TPS signal pattern. The voltage is within range but behaves erratically compared to expected parameters. Mercedes' engine management has uncovered a clue worth investigating in the throttle system.
The 2022 E-Class offers the M254 2.0L turbo-four with 48V EQ Boost (E 350), M256 3.0L turbo-six with ISG (E 450), or the M177 4.0L twin-turbo V8 (AMG E 63). All use direct injection. At 2-4 years old, both software and carbon buildup are viable suspects.
Top Causes of P0121 on the 2022 E-Class
- Carbon buildup on throttle body – DI engines accumulate deposits in 2-4 years. Likelihood: 35%
- ECU software calibration – Mercedes may have released updates. Likelihood: 25%
- Throttle body assembly issue – Internal TPS defect. Likelihood: 20%
- 48V system interaction – ISG transitions affecting throttle data. Likelihood: 12%
- Connector or wiring problem – Corrosion or loose fit. Likelihood: 8%
Symptoms You May Notice
- Check Engine Light on MBUX
- Rough or inconsistent idle
- Hesitation during acceleration
- Reduced power or limp mode
- EQ Boost feels rough
- Cruise control inoperative
How Serious Is This Code?
P0121 is medium severity. Your 2022 E-Class remains drivable with reduced performance. Address it soon—within 1-2 weeks.
Diagnostic Steps
- Scan with XENTRY or Mercedes-compatible scanner
- Check ECU software version and available updates
- Inspect throttle body for carbon deposits
- Monitor TPS voltage alongside ISG/48V data
- Check throttle body connector integrity
- Inspect intake system for boost leaks
Estimated Repair Costs
- Under warranty: $0 (4-year/50,000-mile warranty likely active)
- Throttle body cleaning: $150–$300 (DIY: $15–$25)
- Throttle body replacement: $600–$1,100
- ECU software update: $150–$250 (if out of warranty)
Can You DIY This Fix?
DIY feasibility is low. Check warranty first—the 2022 E-Class should still be under Mercedes' 4-year/50,000-mile warranty. If covered, let the dealer handle it at no cost. If expired, throttle body cleaning is possible for experienced DIYers with a Mercedes-compatible diagnostic tool.