What Does P0121 Mean on a 2024 Jeep Grand Wagoneer?
A P0121 code on your 2024 Jeep Grand Wagoneer indicates the PCM has detected an irregular voltage pattern from the throttle position sensor (TPS). The signal is present but behaves inconsistently with your driving inputs. On a flagship vehicle like the Grand Wagoneer, any engine code deserves immediate professional attention.
The 2024 Grand Wagoneer offers the 6.4L Hemi V8 (port injection) or the new 3.0L Hurricane twin-turbocharged inline-six (direct injection). Both use electronic throttle control with integrated TPS. The Hurricane I6 is particularly noteworthy—its direct injection and twin turbo setup makes it more susceptible to carbon buildup, though at low mileage this is unlikely. Software calibration is the primary suspect on a new vehicle.
Top Causes of P0121 on the 2024 Grand Wagoneer
- PCM software calibration – New powertrains may need throttle mapping updates. Likelihood: 40%
- Factory throttle body defect – Manufacturing issue with the TPS. Likelihood: 25%
- Connector assembly issue – Not fully seated from the factory. Likelihood: 20%
- Electrical interference – The Grand Wagoneer's extensive electronics suite may cause signal noise. Likelihood: 10%
- Carbon buildup – Unlikely at low mileage. Likelihood: 5%
Symptoms You May Notice
- Check Engine Light on
- Rough or inconsistent idle
- Hesitation during acceleration
- Reduced power from V8 or Hurricane I6
- MDS cylinder deactivation may not engage (6.4L)
- Cruise control issues
How Serious Is This Code?
P0121 is medium severity. Your 2024 Grand Wagoneer remains drivable, but any issue on a vehicle in this price class should be resolved immediately. Address it soon—schedule a dealer appointment right away. Full warranty coverage applies.
Diagnostic Steps
- Take the Grand Wagoneer to your Jeep dealer—warranty applies
- Dealer uses wiTECH for full diagnostic analysis
- Check for TSBs and PCM software updates for both engine options
- Inspect throttle body connector and wiring
- Monitor live TPS, boost (Hurricane), and MDS data
- Replace throttle body if hardware fault confirmed
Estimated Repair Costs
- Under warranty: $0 (fully covered by 3-year/36,000-mile basic warranty)
- PCM software update: $0 under warranty
- Throttle body replacement (if out of warranty): $450–$750
Should You DIY This?
DIY feasibility is low. Your 2024 Grand Wagoneer is fully covered under Stellantis' 3-year/36,000-mile basic warranty and 5-year/60,000-mile powertrain warranty. Let the dealer handle everything at no cost. The Hurricane engine is new technology that may require specific software updates only available through wiTECH. DIY work could void warranty coverage on this premium vehicle.