What Does P0121 Mean on a 2023 Kia Soul?
When P0121 appears on your 2023 Kia Soul, our investigators trace it to the throttle position sensor (TPS) delivering voltage within the expected range but with an abnormal pattern. The ECM sees readings that conflict with its calculations from other engine parameters.
The 2023 Soul continues with the 2.0L MPI four-cylinder (147 hp) and CVT. Port injection keeps the throttle body cleaner than GDI alternatives. As one of the final model years, the platform is fully mature.
Common Symptoms to Watch For
- Check engine light on
- Hesitation during acceleration
- Rough idle
- CVT feels unresponsive
- Reduced power during highway merging
- Slightly decreased fuel economy
Top Causes Ranked by Likelihood
- Carbon buildup on throttle body (30%) – At 1-3 years, early deposits from PCV gases are possible. Cost: $100–$225.
- Throttle body assembly defect (25%) – Factory quality issue. Cost: $0 under warranty.
- ECM software calibration (25%) – An available update. Cost: $0 under warranty.
- Wiring or connector issue (15%) – Corrosion or assembly variability. Cost: $0 under warranty.
- Intake system leak (5%) – Gasket or vacuum issue. Cost: $0 under warranty.
How Serious Is This Code?
P0121 is medium severity. Warranty covers the fix. Address this soon.
Diagnostic Path
Dealer KDS diagnostics—free under warranty.
Can You Fix This Yourself?
Full Kia warranty: 5yr/60k basic + 10yr/100k powertrain. Take it to the dealer.
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