Lexus RX 350 Transmission Bucking & Surge (1-2 / 2-3 Upshift): TSB L-SB-0032-19 Explained
If your 2016-2019 RX 350 jerks back and forth right after it shifts from 1st to 2nd or 2nd to 3rd — or rocks back and forth cruising under 46 mph with no shift happening at all — your transmission is almost certainly fine. You're feeling a known ECM software issue covered by Lexus Technical Service Bulletin L-SB-0032-19 (revised September 26, 2019; Canadian equivalent L-TCI-5285). The fix is a free ECM reflash with revised logic — no transmission parts, no fluid, no teardown.
Master Tech Takeaway
This is a software problem, not a mechanical one. Do not let anyone sell you a transmission flush, a torque converter, or a valve body for this complaint. If your RX 350 matches the two conditions below, the answer is the L-SB-0032-19 ECM reflash — it takes under an hour, and under the 48-month/50,000-mile basic warranty (80,000 km in Canada) it costs you nothing.
Affected Models
Applies to 4th-generation RX models with the 2GR-FKS 3.5L V6 and the UA80E 8-speed automatic.
The Two Conditions (Know Which One You Have)
The bulletin describes two distinct symptoms. Matching your complaint to the right one is how a technician confirms the TSB applies — check both:
Condition 1: Bucking on Upshift
A bucking feeling — back-and-forth jerking that comes right after a shift, then dissipates quickly. Happens specifically on the 1-2 and/or 2-3 upshifts, typically at light throttle leaving a stop or accelerating gently.
Condition 2: Surge in Lock-Up (0-46 MPH)
A surge feeling — back-and-forth rocking not associated with any transmission shift. Occurs while traveling 0-46 mph with the transmission in 3rd through 8th gear and the torque converter in full lock-up. Feels like the car can't decide how much power to deliver.
Root Cause: ECM Logic, Not the Transmission
The 8-speed UA80E shifts early and locks the torque converter aggressively to maximize fuel economy. In the original calibration, the Engine Control Module's torque management during those early 1-2 and 2-3 shifts — and its fuel/ignition strategy while the converter is in full lock-up — produced an oscillation: power cuts, power returns, cuts again. You feel it as bucking or surging. Lexus modified the ECM logic to smooth the torque delivery through those transitions. The flash reprogramming installs that revised calibration, and the bulletin requires an Authorized Modifications Label under the hood documenting the new calibration ID.
3 Things Your Dealer May Not Tell You
1. "Could not duplicate" is the #1 outcome — ride along
This complaint lives at light throttle and low speed, exactly the conditions a tech may not reproduce on a quick loop. If you drop the car off cold and just describe it, expect a "could not duplicate." Insist on a road test with you driving, and point to the TSB number directly — L-SB-0032-19. Service advisors know this bulletin well.
2. Most of these cars are out of warranty now — know the real price
The reflash was free under the 48-month/50,000-mile basic warranty (80,000 km in Canada), but 2016-2019 RXs are largely past that in 2026. Out of warranty, the job is 0.5-1.0 hour of labor — roughly $150-$250 — for an ECM flash. That's still a fraction of any transmission repair, and some dealers goodwill it if you're a regular customer. Ask.
3. This TSB doesn't cover every shift complaint
Hesitation from a stop or on reacceleration is a different bulletin (L-SB-0109-17). Harsh shifts at high mileage with dark fluid is a maintenance issue, not software. And if the bucking happens at highway speed or with a flashing check-engine light, stop driving and get it diagnosed — that's not this TSB.
TSB Details
| US Bulletin | L-SB-0032-19 (Rev1: Sep 26, 2019) |
|---|---|
| Canadian Bulletin | L-TCI-5285 |
| NHTSA TSB # | 10166041 |
| Original Issue Date | July 2, 2019 |
| Title | "Vehicle Bucking on 1-2 and/or 2-3 Upshifts and Surge Between 0-46 mph" |
| Component | Powertrain — ECM (PCM) calibration |
| Repair Procedure | Flash reprogram ECM with new calibration file (battery held at 13.5V in Power Supply Mode); install Authorized Modifications Label; road test to confirm |
| Parts Replaced | None — software only |
What To Do If Your RX 350 Bucks or Surges
- Confirm the pattern. Bucking right after the 1-2 or 2-3 shift, or rocking at steady speed under 46 mph with no shift occurring. Note the speed, gear, and throttle when it happens.
- Call your Lexus dealer and reference TSB L-SB-0032-19 (Canada: L-TCI-5285) by number. Ask whether the revised ECM calibration has already been applied to your VIN.
- Road test with the technician and demonstrate the exact condition — light throttle, 1-2 and 2-3 upshifts, and steady cruise under 46 mph.
- Get the reflash. The ECM is reprogrammed with the new calibration, an Authorized Modifications Label is installed under the hood, and the car is road-tested to confirm. Check for the label afterward — it's your proof the update was done.
Master Tech Recommended Tools
The exact tools a Master Tech uses for transmission diagnostics and the ECM reflash procedure. As an Amazon Associate, we earn from qualifying purchases at zero extra cost to you.
Autel MaxiAP AP200 Bluetooth OBD2 Scanner
Read transmission and ECM codes, check live data, and verify no stored DTCs before booking the TSB reflash — rules out real mechanical faults.
NOCO Genius5 5A Smart Battery Charger
The TSB requires battery voltage held at 13.5V in Power Supply Mode during the ECM flash — this is the maintainer pros use so a reflash never bricks a module.
Frequently Asked Questions
What does Lexus TSB L-SB-0032-19 fix?+
L-SB-0032-19 (revised September 26, 2019) fixes two conditions on 2016-2019 RX 350 and RX 350L: a bucking feeling (back-and-forth jerking right after the shift) following 1-2 and/or 2-3 upshifts, and a surge feeling (back-and-forth rocking not tied to shifts) between 0-46 mph with the transmission in 3rd-8th gear and the torque converter in full lock-up. The fix is revised ECM logic installed by flash reprogramming.
Is my RX 350 transmission damaged if it bucks on upshifts?+
Almost certainly not. The bucking and surge described in L-SB-0032-19 are caused by ECM calibration logic, not worn clutches or a failing transmission. The bulletin reprograms the engine control module with updated software — no transmission parts are replaced.
How much does the L-SB-0032-19 update cost out of warranty?+
Under the 48-month/50,000-mile basic warranty (80,000 km in Canada) the reflash is free. Most 2016-2019 RX 350s are past that now — out of warranty, dealers typically charge 0.5 to 1.0 hour of labor for the ECM reflash, roughly $150-$250. Still far cheaper than any transmission work.
Will the bucking come back after the ECM reflash?+
The revised calibration permanently changes the shift and lock-up logic, so the specific bucking/surge conditions in the bulletin do not return. Note the TSB only covers the two described conditions — a harsh shift from worn fluid or other causes is a separate diagnosis.