What Does P0121 Mean on a 2022 GMC Sierra?
A P0121 code on your 2022 GMC Sierra means the ECM has detected an abnormal TPS signal pattern. The voltage is within range but doesn't correlate with your driving inputs. Your Sierra's engine management has flagged a throttle anomaly.
The 2022 Sierra offers the 2.7L turbo-four, 5.3L V8, or 6.2L V8. The V8s feature GM's dual-injection system (port + direct), which helps keep the throttle body cleaner. The 2.7L uses direct injection only. At 2-4 years old, both software and carbon buildup are possible causes.
Top Causes of P0121 on the 2022 Sierra
- Carbon buildup on throttle body – More likely on the 2.7L DI-only engine. Likelihood: 35%
- ECM software calibration – GM may have updates. Likelihood: 25%
- Throttle body assembly issue – Internal TPS fault. Likelihood: 20%
- Connector or wiring problem – Truck vibration and corrosion. Likelihood: 15%
- DFM interaction (V8s) – Cylinder deactivation affecting throttle. Likelihood: 5%
Symptoms You May Notice
- Check Engine Light on
- Rough or inconsistent idle
- Hesitation during acceleration
- Reduced towing power
- DFM not engaging
- Cruise control issues
How Serious Is This Code?
P0121 is medium severity. Your 2022 Sierra remains drivable. Address it soon—within 1-2 weeks.
Diagnostic Steps
- Scan with GDS2 or OBD-II scanner
- Identify your engine option
- Inspect throttle body for carbon
- Monitor TPS voltage
- Check connector and wiring
- Check for TSBs
Estimated Repair Costs
- Under warranty: $0 (GM 3-year/36,000-mile may still apply)
- Throttle body cleaning: $100–$220 (DIY: $10–$20)
- Throttle body replacement: $350–$650
Can You DIY This Fix?
DIY feasibility is moderate. Check warranty—the 2022 Sierra may be under GM's 3-year/36,000-mile warranty. The 5-year/60,000-mile powertrain warranty is active. Truck engine bays are spacious. After cleaning, disconnect battery 30 minutes, reconnect, idle 15 minutes for ECM relearn.