What Does P0122 Mean on a 2023 Toyota Highlander?
If your 2023 Toyota Highlander is displaying a P0122 trouble code, the ECM has detected that the throttle position sensor circuit is generating a signal below the 0.2-volt minimum threshold. The valid TPS signal range is 0.5 to 4.5 volts. When the signal collapses below that floor, the ECM cannot determine throttle position and immediately activates a failsafe mode that restricts engine output and may trigger multiple warning lights across the instrument cluster.
The 2023 Highlander carries a significant powertrain distinction that sets it apart from earlier generations: Toyota eliminated the 3.5L V6 2GR-FKS engine that had powered the Highlander for years and replaced it exclusively with the 2.4L turbocharged four-cylinder T24A-FTS engine producing 265 horsepower and 309 lb-ft of torque. A 2.5L Hybrid variant is also available with the Atkinson-cycle engine and electric motor system producing 243 combined horsepower. This engine transition was controversial among Highlander buyers but represents a clear direction toward turbocharged efficiency. Both powertrains use drive-by-wire electronic throttle control with an integrated TPS assembly.
As a 2023 model, your Highlander is almost certainly within full factory warranty coverage. Toyota provides 3-year/36,000-mile bumper-to-bumper, 5-year/60,000-mile powertrain, and 8-year/80,000-mile federal emissions warranty. P0122 on a vehicle this new should be a dealer warranty repair — your out-of-pocket cost should be $0. This is a new engine architecture and any TPS-related issues at this age almost certainly reflect manufacturing or early-production quality concerns that Toyota is responsible for correcting.
Symptoms You May Be Experiencing
P0122 on a 2023 Highlander may feel particularly alarming because the vehicle is nearly new. The 2.4L turbocharged engine has different throttle response characteristics than the previous V6 — its torque curve peaks earlier and more sharply — making a sudden TPS circuit failure feel especially dramatic.
- Limp mode with significantly reduced power — The 2.4T Highlander normally delivers strong mid-range torque. In limp mode, this disappears entirely, leaving the vehicle struggling to maintain normal traffic speeds.
- Check engine light plus stability system warnings — VSC, traction control, and the check engine light typically appear simultaneously because stability systems depend on accurate throttle data.
- Sluggish, unresponsive accelerator pedal — The drive-by-wire system cannot open the throttle properly without a valid TPS signal, resulting in minimal or no throttle response.
- Stalling at idle or when coming to a stop — Without TPS feedback, idle management becomes unreliable.
- Hybrid model behavior (2023 Highlander Hybrid) — On the hybrid variant, TPS circuit failure may trigger additional hybrid system warnings and restrict both gasoline and electric power delivery.
Some 2023 Highlander owners report P0122 appearing during specific driving conditions — cold morning starts, highway driving at speed, or after the vehicle sits overnight. These intermittent patterns on a new vehicle are often connector-related manufacturing issues or early-production throttle body defects. Document when and how the fault appears to help your dealer technician investigate more efficiently.
Top Causes of P0122 on the 2023 Highlander
On a 2-3 year old vehicle with the newly introduced 2.4L turbo engine, early-production factors dominate the cause profile:
1. Throttle Body Connector Seating or Production Assembly Issue (Most Likely — approximately 38-42% of cases)
The 2.4L T24A-FTS is a relatively new engine in the Highlander application, having debuted in the RAV4 before appearing in the Highlander. The connector assembly process at the factory can leave some connectors marginally seated, with insufficient terminal engagement. Vibration from the turbocharged engine can worsen this over months. This is a manufacturing-side issue that Toyota is responsible for correcting under warranty.
2. Throttle Body Internal TPS Defect (Likely — approximately 33-36% of cases)
The TPS element integrated into the 2.4L turbo throttle body can develop early-production defects — internal shorts, open circuits in the potentiometer element, or component-level quality variations. These defects may not manifest immediately at delivery but appear within the first year or two of operation. On a 2023 vehicle, this is clearly a warranty item.
3. Wiring Harness Routing Issue near Turbocharger (Moderate — approximately 18% of cases)
The 2.4L T24A-FTS is a turbocharged engine, meaning the engine bay runs hotter in the turbocharger area than a naturally aspirated engine. If the wiring harness from the throttle body to the ECM is routed near the turbocharger or its hot-side plumbing, early insulation degradation is possible even on a 2-3 year old vehicle. Check with your Toyota dealer whether any TSBs address harness routing corrections for the 2023 Highlander 2.4T.
4. ECM Software or Calibration Issue (Less Likely — approximately 5-7% of cases)
New engine platforms sometimes have ECM calibration edge cases where voltage thresholds are not correctly interpreted under specific conditions. Toyota addresses these through software updates at the dealer. If no hardware fault is found, a Techstream software update should be the next investigative step.
5. Moisture Intrusion (Rare — approximately 2% of cases)
Even on new vehicles, water intrusion from heavy rain or high-pressure washing near the throttle body connector is possible and can cause TPS circuit failure.
Estimated Repair Costs Under Warranty
Your 2023 Highlander is under the 3-year/36,000-mile bumper-to-bumper warranty, which means the P0122 repair cost to you should be $0 if the fault is a manufacturing or materials defect. This is the expectation for a vehicle this new.
For reference, out-of-warranty costs for this repair:
- Throttle body connector cleaning or repair: $50-$150
- Throttle body replacement (2.4L turbo T24A-FTS): $340-$560 — The turbo variant uses a different throttle body than naturally aspirated engines and parts costs reflect this.
- Throttle body replacement (2.5L Hybrid): $320-$520
- Wiring harness repair: $150-$350
- ECM software update: Typically free at dealer
After any throttle body work, the Toyota idle relearn procedure is required. On the 2023 Highlander, Toyota Techstream is the preferred method for throttle position initialization, which your dealer will perform as part of the repair process.
Urgency and Warranty Guidance
P0122 is always high-severity and immediate-urgency, regardless of vehicle age. Limp mode on the 2023 Highlander eliminates the 2.4T engine's power advantage and leaves you without adequate acceleration for safe highway driving.
Contact your Toyota dealer immediately. As a 2023 vehicle, you are within the full bumper-to-bumper warranty period. Request a service appointment and a loaner vehicle if the repair cannot be completed same-day. Toyota's dealer network is obligated to repair this defect at no charge. Keep documentation of the visit for your warranty history file.
Also ask the dealer to check for any open Technical Service Bulletins affecting the 2023 Highlander 2.4T engine and throttle system. New engine introductions often generate TSBs as Toyota identifies and addresses early-production issues across the fleet.
How AutoDetective AI Can Help
Even on a new vehicle, AutoDetective.ai adds value by helping you document and understand exactly what P0122 means for your 2023 Highlander. Our AI detective confirms the diagnosis, identifies whether related codes may be present, and generates a clear summary you can bring to the dealership. Going to the dealer informed about P0122 helps ensure the root cause is addressed — not just the code cleared — so the fault does not reappear weeks later.