Investigating P0121 on Your 2020 Dodge Challenger
When your 2020 Dodge Challenger throws a P0121, the PCM has discovered that the throttle position sensor signal is behaving unpredictably. The voltage stays within acceptable limits, but the pattern doesn't track with your accelerator input—our investigation reveals that the throttle body's signal integrity is compromised.
The 2020 Challenger is available with the 3.6L Pentastar V6, 5.7L Hemi V8 (R/T), 6.4L SRT Hemi (Scat Pack), and supercharged variants. All engines use port fuel injection and electronic throttle control with dual TPS signals integrated into the throttle body assembly.
Symptoms on the Road
- Check engine light illuminated
- Throttle response feels delayed or inconsistent
- Rough idle, especially when cold
- Hesitation or bog during hard acceleration
- MDS transitions feel rough or jerky on Hemi models
Ranked Causes
- Carbon deposits on throttle plate and bore – At 4–6 years old, PCV vapors have had time to coat the throttle body. Challengers used primarily for spirited driving may see less buildup due to frequent wide-open throttle, but city-driven examples accumulate deposits faster. Likelihood: 45%
- Worn throttle body assembly – The internal TPS or actuator motor develops wear. This is more common at higher mileage. Likelihood: 25%
- Connector or wiring degradation – Heat cycling and age cause corrosion on connector pins or wire insulation breakdown. Likelihood: 15%
- Intake or vacuum leak – Aged gaskets or cracked PCV hoses allow unmetered air into the intake. Likelihood: 10%
- PCM adaptation drift – Long-term throttle body learning values have drifted beyond acceptable thresholds. Likelihood: 5%
What Will It Cost?
- Throttle body cleaning: $80–$150 (shop) / $10–$20 (DIY)
- Throttle body replacement: $250–$550 parts and labor
- Wiring/connector repair: $100–$250
- PCV valve/hose repair: $50–$150
DIY Feasibility: High
Your 2020 Challenger is likely out of the 3-year/36,000-mile basic warranty but should be within the 5-year/60,000-mile powertrain warranty if under 60,000 miles. The federal emissions warranty (8 years/80,000 miles) may also cover this repair. For DIY, the Challenger's throttle body is easily accessible—especially on the Hemi engines where it sits prominently atop the intake manifold. Clean it, perform a throttle relearn (battery disconnect 20–30 minutes, then idle for 15 minutes), and clear the code.
How AutoDetective AI Can Help
AutoDetective's AI analyzes your Challenger's engine variant, mileage, and freeze frame data to determine whether you're dealing with simple carbon buildup or a failing throttle body. Get your free diagnosis before buying parts.