What Does P0121 Mean on a 2023 Chevrolet Tahoe?
When a P0121 code appears on your 2023 Chevrolet Tahoe, our diagnostic investigation reveals the throttle position sensor (TPS) is sending voltage signals within the normal range but with an abnormal pattern. The ECM identifies a mismatch between TPS data and calculated engine parameters—the sensor story doesn't align with the evidence from other sources.
Your 2023 Tahoe runs on the refined T1XX platform with engine choices including the 5.3L V8 (355 hp), 6.2L V8 (420 hp), and 3.0L Duramax turbo-diesel (277 hp). The V8 engines benefit from dual injection (direct + port), which reduces carbon buildup compared to direct-injection-only designs. By 2023, GM had refined the T1XX calibrations significantly since the 2021 launch.
Common Symptoms to Watch For
- Check engine light or Reduced Engine Power warning
- Hesitation or stumble during acceleration
- Rough or fluctuating idle
- Reduced throttle response when towing
- Dynamic Fuel Management may disengage unexpectedly
- Transmission may shift at inappropriate times
Top Causes Ranked by Likelihood
- Carbon buildup on throttle body (35%) – Even with dual injection on the V8s, PCV gases and normal combustion byproducts deposit carbon on the throttle bore over time. The diesel is more susceptible. Cost: $150–$300.
- Throttle body assembly failure (25%) – An internal TPS defect creating dead spots or erratic voltage. Cost: $0 under warranty; $350–$600 otherwise.
- ECM software calibration (20%) – While the T1XX is more mature by 2023, updated calibrations are still released. Cost: $0 under warranty.
- Wiring or connector issue (15%) – Connector corrosion, pin seating, or harness damage from vibration. Cost: $0 under warranty; $100–$300 otherwise.
- Intake system leak (5%) – A gasket or boot issue creating unmetered airflow. Cost: $0 under warranty; $100–$350 otherwise.
How Serious Is This Code?
P0121 is medium severity. For a vehicle frequently used for towing and family hauling, reliable throttle response is critical. The Reduced Engine Power failsafe is the primary concern. Schedule service soon.
Diagnostic Path
Your 2023 Tahoe is under warranty—take it to a Chevrolet dealer. They'll use GDS2 to read live TPS data, check for companion codes, verify ECM software version, and search for applicable TSBs. If you want preliminary data, any quality OBD2 scanner can read TPS voltage during throttle sweeps.
Can You Fix This Yourself?
Your 2023 Tahoe is fully covered under GM's 3yr/36k bumper-to-bumper warranty, and the 5yr/60k powertrain warranty also applies. Take it to the dealer—diagnosis and repair are free. There's no financial reason for DIY on a vehicle with active warranty coverage.
Get a Free AI Diagnosis
Prepare for your dealer visit with confidence. Enter your 2023 Tahoe's details into AutoDetective's free AI diagnosis tool for a preliminary analysis you can discuss with your service advisor.