P0120 on Your 2024 Buick Envision: The Full Investigation
A "Reduced Engine Power" warning on your brand-new 2024 Envision is an unwelcome surprise. P0120 points to a throttle position sensor circuit malfunction — the ECU is receiving signals from the TPS circuit that fall outside the expected voltage range. Your 2024 Envision runs GM's 2.0L turbocharged LSY engine on the E2XX platform, where the electronic throttle body integrates the position sensor directly into the assembly. On a vehicle this new, the trail of evidence leads toward manufacturing issues or software calibration rather than wear.
Warning Signs
- "Reduced Engine Power" warning displayed
- Check engine light on
- Acceleration limited to crawling speed
- Throttle pedal feels disconnected from the engine
- Idle speed may fluctuate or stall
Most Probable Causes
1. Factory Throttle Body Defect
At low mileage, an internal defect in the electronic throttle body — defective potentiometer track, weak motor winding, or contamination from manufacturing — is the primary suspect. Warranty replacement resolves this completely.
2. Software Calibration Update
GM regularly releases ECU calibration updates after production. A TAC system or throttle body adaptation update may have been released since your Envision was built.
3. Assembly Connector Issue
A throttle body connector not fully latched during factory assembly can work loose with road vibration, creating intermittent TPS signal faults.
4. Harness Routing Problem
Wiring pinched between engine components during assembly can develop conductor damage over initial break-in miles.
5. Pedal Sensor Factory Defect
The dual-sensor accelerator pedal rarely fails new, but a manufacturing outlier can produce signals that the ECU interprets as a TPS circuit fault.
Diagnostic Steps
- Dealer scan with GDS2 for full diagnostic and TSB lookup
- Check for pending software calibration updates
- Verify throttle body connector seating
- Review live TPS and APP sensor data
- Inspect harness routing for pinch points
Repair Costs
- All repairs under warranty: $0
- Throttle body replacement (if out of pocket): $250–$500
- Software update: $0 under warranty
Can I Drive With P0120?
Reduced Engine Power mode makes normal driving impossible. Use OnStar roadside assistance to arrange a tow to your Buick dealer. Throttle system faults are safety-critical and warrant priority service.
DIY vs Professional
Dealer only. Your 2024 Envision is fully covered under GM's 3-year/36,000-mile bumper-to-bumper and 5-year/60,000-mile powertrain warranties. All throttle system repairs will be handled at no cost.
Frequently Asked Questions
Is P0120 dangerous on my 2024 Envision?
The throttle system is safety-critical, but the Reduced Engine Power mode is the ECU's way of protecting you. The vehicle limits power rather than allowing unpredictable throttle behavior. Get it to the dealer promptly.
Will this repair be free?
Yes. Your 2024 Envision is under full factory warranty. Throttle body and related electrical repairs are covered at no cost to you.
How long will the repair take?
Software updates are same-day. Throttle body replacement is typically same-day if the part is in stock, or 1-2 business days if ordered.
Should I be concerned about recurring issues?
If the root cause is properly identified and repaired, P0120 should not recur. If it does, the dealer needs to investigate deeper — possibly the wiring harness or ECU.