P0121 on Your 2023 Toyota Highlander
Your 2023 Highlander (XU70) has triggered P0121 — throttle position sensor range/performance. This model year introduced the turbocharged 2.4L T24A-FTS engine replacing the 3.5L V6, along with the continued 2.5L hybrid option. The new turbo engine's electronic throttle body is reporting an abnormal TPS pattern. On a vehicle this new, software and manufacturing issues lead the suspect list.
What You're Noticing
- Check engine light on
- Throttle response feels slightly off
- Idle may be marginally unsteady
- 8-speed auto shift points seem slightly wrong
- Minor hesitation from stops
Common Causes (Ranked by Likelihood)
1. ECU Software Calibration
The 2023 Highlander introduced a new engine — the 2.4L turbo. First-year engine installations frequently receive software refinements that adjust TPS performance windows and adaptation parameters.
2. Throttle Body Manufacturing Variance
A new powertrain means new throttle body specifications. An occasional unit with marginal sensor calibration can trigger P0121. Warranty replacement handles this.
3. Connector/Wiring Issue
A new engine installation on an existing platform can occasionally have connector or wiring routing issues that weren't present on the previous V6 configuration.
4. Early Carbon Deposits
The 2.4L turbo uses direct injection only (no D-4S), making it more susceptible to carbon than the previous D-4S V6. Though unlikely at low mileage, aggressive short-trip driving could accelerate deposits.
5. Accelerator Pedal Module
A manufacturing defect in the APP sensor is rare but possible, producing signal conflicts.
Diagnostic Steps
- Toyota dealer scans with Techstream
- Check for TSBs specific to the 2023 Highlander 2.4T
- Verify connector engagement at throttle body
- Monitor TPS live data for smooth voltage progression
- Check for ECU software updates
Repair Costs
- All repairs under warranty: $0
- Software update (out of pocket): $100–$200
- Throttle body replacement (out of pocket): $350–$600
Can I Drive With P0121?
Yes. No limp mode. Safe for daily driving including passengers. Schedule a dealer visit within a week or two.
DIY vs Professional
Your 2023 Highlander is under Toyota's 3-year/36,000-mile warranty. Take it to the dealer — free repair. Do not attempt DIY on a vehicle under warranty.
Frequently Asked Questions
Is P0121 related to the new 2.4L turbo engine?
Possibly. New engine installations on existing platforms can need calibration refinements. This is normal for first-year powertrain changes.
Is the 2.4L turbo more prone to carbon than the old V6?
The 2.4T uses direct injection only, while the 3.5L V6 had D-4S. Over time, the turbo may accumulate more intake carbon, though it's too early to see this on 2023 models.
Will P0121 affect the 8-speed transmission?
The 8-speed uses throttle data for shift scheduling. Fixing P0121 restores optimal shift timing.
Does Toyota provide a loaner for warranty repairs?
Many Toyota dealers offer loaner vehicles for warranty work. Call ahead when scheduling your appointment.