What Does P0121 Mean on a 2024 Mazda3?
A P0121 code on your 2024 Mazda3 signals that the PCM has detected an abnormal TPS voltage pattern. The signal is present but doesn't match expected behavior. On a new Mazda3, this should be addressed under warranty.
The 2024 Mazda3 offers the Skyactiv-G 2.5L NA or 2.5T turbo, both with direct injection. The electronic throttle body integrates the TPS. At low mileage, software calibration is the primary suspect.
Top Causes of P0121 on the 2024 Mazda3
- PCM software calibration – Software updates for throttle mapping. Likelihood: 40%
- Factory throttle body defect – Manufacturing issue. Likelihood: 25%
- Connector assembly issue – Not properly seated. Likelihood: 20%
- Electrical interference – Signal noise. Likelihood: 10%
- Carbon buildup – Unlikely at low mileage. Likelihood: 5%
Symptoms You May Notice
- Check Engine Light on
- Inconsistent idle
- Hesitation during acceleration
- Reduced turbo response (2.5T)
- Cruise control issues
How Serious Is This Code?
P0121 is medium severity. Your 2024 Mazda3 remains drivable. Schedule a dealer visit soon—within the week. Full warranty applies.
Diagnostic Steps
- Take the Mazda3 to your dealer—warranty covers this
- Dealer uses Mazda IDS for diagnostics
- Check for TSBs and software updates
- Inspect throttle body and connector
- Monitor live TPS data
Estimated Repair Costs
- Under warranty: $0 (Mazda 3-year/36,000-mile basic warranty)
- PCM update: $0 under warranty
- Throttle body replacement (if out of warranty): $300–$550
Should You DIY This?
DIY feasibility is low. Your 2024 Mazda3 is under Mazda's 3-year/36,000-mile basic warranty and 5-year/60,000-mile powertrain warranty. Let the dealer handle it at no cost.