What Does P0121 Mean on a 2024 Jeep Grand Cherokee?
A P0121 code on your 2024 Jeep Grand Cherokee signals that the PCM has detected an abnormal voltage pattern from the throttle position sensor (TPS). The signal is present and within range, but it doesn't behave as expected for your driving conditions. On a new Grand Cherokee, this is an unusual finding that warrants prompt dealer attention.
The 2024 Grand Cherokee (WL) offers multiple powertrains: the 3.6L Pentastar V6 (port + direct injection), 5.7L Hemi V8, and the 4xe plug-in hybrid (2.0L turbo + electric motors). Each uses electronic throttle control with an integrated TPS. On a low-mileage vehicle, carbon buildup is unlikely—software calibration and factory quality issues are the primary suspects.
Top Causes of P0121 on the 2024 Grand Cherokee
- PCM software calibration – New model year software may need updating. Likelihood: 35%
- Factory throttle body defect – Manufacturing issue with the TPS assembly. Likelihood: 25%
- Connector not properly seated – Assembly-line oversight. Likelihood: 20%
- Electrical interference – Particularly on the 4xe hybrid with its additional electronics. Likelihood: 15%
- Carbon buildup – Unlikely at low mileage. Likelihood: 5%
Symptoms You May Notice
- Check Engine Light illuminated
- Rough or inconsistent idle
- Hesitation on acceleration
- Reduced engine power
- 4xe hybrid: may affect electric/gas transition behavior
- Cruise control inoperative
How Serious Is This Code?
P0121 is medium severity. Your 2024 Grand Cherokee remains drivable, but any check engine code on a new vehicle deserves prompt attention. Address it soon—schedule a dealer visit within the week. Full warranty coverage makes this a no-cost repair.
Diagnostic Steps
- Take the vehicle to your Jeep dealer—warranty covers this
- The dealer will use wiTECH for full diagnostic analysis
- Check for TSBs and PCM software updates for the 2024 Grand Cherokee
- Inspect throttle body connector and wiring for factory quality
- Monitor live TPS data across all driving conditions
- For 4xe models: verify no interference from hybrid system electronics
Estimated Repair Costs
- Under warranty: $0 (fully covered by Stellantis 3-year/36,000-mile basic warranty)
- PCM software update: $0 under warranty
- Throttle body replacement (if out of warranty): $400–$700
Should You DIY This?
DIY feasibility is low. Your 2024 Grand Cherokee is fully covered under Stellantis' 3-year/36,000-mile basic warranty and 5-year/60,000-mile powertrain warranty. Let the dealer handle it at no cost. PCM updates require the wiTECH diagnostic system. DIY work on a new vehicle could jeopardize warranty coverage.