What Does P0121 Mean on a 2024 Mercedes-Benz GLE?
A P0121 code on your 2024 Mercedes-Benz GLE (W167) signals that the ECU has detected an abnormal TPS voltage pattern. The signal exists but doesn't match expected behavior. On Mercedes' mid-size luxury SUV, any engine management issue warrants prompt dealer attention.
The 2024 GLE offers the M254 2.0L turbo-four with 48V EQ Boost (GLE 350), M256 3.0L turbo-six with ISG (GLE 450), or the M176 4.0L twin-turbo V8 (GLE 580/AMG GLE 63). All use direct injection. The mild-hybrid system's 48V components add powertrain complexity. At low mileage, software calibration is the primary suspect.
Top Causes of P0121 on the 2024 GLE
- ECU software calibration – Software updates common on updated models. Likelihood: 40%
- Factory throttle body defect – Manufacturing issue with TPS. Likelihood: 25%
- Connector assembly issue – Not properly seated. Likelihood: 20%
- 48V/ISG interaction – Torque transitions affecting throttle data. Likelihood: 10%
- Carbon buildup – Unlikely at low mileage. Likelihood: 5%
Symptoms You May Notice
- Check Engine Light on MBUX
- Inconsistent idle
- Hesitation on acceleration
- EQ Boost/ISG transitions feel rough
- Reduced power message
- Driver-assist features may be affected
How Serious Is This Code?
P0121 is medium severity. Your 2024 GLE remains drivable. Schedule a dealer visit soon—within the week. Full warranty applies.
Diagnostic Steps
- Take the GLE to your Mercedes dealer—warranty covers this
- Dealer uses XENTRY for comprehensive diagnostics
- Check for software updates and SCN coding
- Inspect throttle body and connector
- Monitor TPS and hybrid system data
- Replace throttle body if fault confirmed
Estimated Repair Costs
- Under warranty: $0 (Mercedes 4-year/50,000-mile warranty)
- ECU update: $0 under warranty
- Throttle body replacement (if out of warranty): $600–$1,100
Should You DIY This?
DIY feasibility is low. Your 2024 GLE is fully covered under Mercedes' 4-year/50,000-mile warranty. Let the dealer handle it at no cost.