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2021 IS 300 Hesitation and Rough Shifts at Low Speeds

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Kim L. · rep 0 · May 22, 4:46 AM · 1 replies · solved · Question

Vehicle: 2021 Lexus IS 300 F Sport

I've noticed some hesitation and slightly rough shifts, particularly from 1st to 2nd gear, in my 2021 Lexus IS 300 F Sport. It's most apparent when the car is cold or in stop-and-go traffic. It's not a violent jolt, but it's definitely not as smooth as I'd expect from a Lexus.

The car only has about 30,000 miles on it. Is this something that could be normal break-in behavior, or should I be concerned? Are there any known TSBs for transmission behavior on the 2021 IS 300?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:46 AM

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ClearTheCode admin answer:

Experiencing hesitation and rough shifts in your 2021 Lexus IS 300 F Sport, especially at low speeds or when cold, is something worth investigating, even with relatively low mileage. While Lexus transmissions are generally very reliable, here's what could be happening:

  1. Transmission Adaptive Learning: Modern automatic transmissions, including those in Lexus vehicles, have adaptive learning capabilities. This means the transmission control unit (TCU) learns your driving style over time and adjusts shift points and pressures accordingly. Sometimes, if driving patterns change, or after a battery disconnect, the system might need to 're-learn,' leading to temporary rougher shifts. This usually smooths out after a few hundred miles.
  2. Software Updates: Similar to infotainment systems, the TCU can have software updates available that improve shift logic and address minor drivability concerns. A Lexus dealership can check for and apply any relevant updates.
  3. Transmission Fluid Level/Quality: Although your car has low mileage, an incorrect transmission fluid level or, less likely, degraded fluid could contribute to shifting issues. This should be checked by a professional, as many modern transmissions are sealed units without an easily accessible dipstick.
  4. Throttle Body/Sensor Issues: Sometimes, issues with the throttle body or accelerator pedal position sensor can indirectly affect transmission behavior by sending incorrect signals to the engine and transmission control units.
  5. TSBs (Technical Service Bulletins): It's definitely worth asking your Lexus dealership if there are any TSBs specifically addressing transmission shift quality for the 2021 IS 300. Manufacturers often issue these for minor but common drivability complaints.

When to See a Shop: If the rough shifts are persistent, worsen over time, or are accompanied by warning lights (like a Check Engine Light, which might show codes like P0700 for a transmission control system malfunction), you should have your vehicle inspected by a Lexus technician. They can perform a diagnostic scan for any stored transmission-related fault codes and assess the transmission's health and fluid condition.

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