What Does P0121 Mean on a 2024 Chevrolet Silverado?
A P0121 case on your 2024 Chevrolet Silverado tells our diagnostic investigators that the throttle position sensor (TPS) is delivering voltage readings within the normal range but with an abnormal performance pattern. The ECM detects a mismatch between the TPS signal and what it expects based on MAP sensor data, engine load calculations, and accelerator pedal position.
The 2024 Silverado rides on GM's T1XX platform and offers multiple engine options: a 2.7L turbo-four (310 hp), the 5.3L V8 (355 hp), the 6.2L V8 (420 hp), and the 3.0L Duramax turbo-diesel. Each uses electronic throttle control with an integrated TPS in the throttle body. The specific engine in your Silverado affects which failure patterns are most likely.
Common Symptoms to Watch For
- Check engine light or Reduced Engine Power message
- Hesitation or stumbling during acceleration
- Rough or surging idle
- Delayed throttle response when towing or hauling
- Transmission may shift erratically due to inconsistent throttle input
- Active Fuel Management or Dynamic Fuel Management may not engage properly
Top Causes Ranked by Likelihood
- Throttle body manufacturing defect (30%) – On a current-year vehicle, the most likely cause is a factory defect in the electronic throttle body or its internal TPS element. GM will address this under warranty. Cost: $0 under warranty.
- ECM software calibration (30%) – GM frequently releases updated calibrations for new model year trucks. A PCM reflash may resolve the code without parts replacement. Cost: $0 under warranty.
- Wiring harness or connector issue (20%) – Truck chassis flex, especially during towing or off-road use, can stress the throttle body harness or connector. Manufacturing defects in pin crimps are also possible. Cost: $0 under warranty.
- Carbon buildup on throttle body (15%) – Less common at low mileage, but the 2.7L turbo's direct injection design can accelerate deposits. The V8 engines with port injection are less susceptible. Cost: $150–$300 if not warranty-covered.
- TAC module communication fault (5%) – The Throttle Actuator Control module on GM trucks can occasionally develop communication issues with the ECM. Cost: $0 under warranty.
How Serious Is This Code?
P0121 is medium severity, but on a full-size truck used for towing or hauling, the impact is amplified. The Reduced Engine Power mode can leave you significantly underpowered. Schedule a dealer appointment soon—this is a warranty-covered repair on your 2024 model.
Diagnostic Path
Take your 2024 Silverado to a Chevrolet dealer. They'll use GDS2 (GM's factory diagnostic system) to monitor live TPS data, check for related TAC codes, and verify ECM software version. If diagnosing yourself, a quality scan tool can display TPS voltage during throttle sweeps—look for dropouts or erratic signals.
The dealer will also check GM's Technical Service Information for any bulletins related to your engine option and build date. First-year calibration updates are common and often resolve intermittent throttle codes.
Can You Fix This Yourself?
Your 2024 Silverado is covered by GM's 3yr/36k bumper-to-bumper warranty and 5yr/60k powertrain warranty. Go to the dealer—this repair should cost nothing. Attempting DIY repairs on a vehicle under warranty is unnecessary and could complicate your coverage.
Get a Free AI Diagnosis
Heading to the dealer? Let AutoDetective's AI analyze your 2024 Silverado's specific symptoms and engine configuration first. Our free diagnosis gives you the information to have a productive conversation with your service advisor.