2021 Toyota Redundant Sienna

While braking, the brakes will momentarily stop working. This has happened multiple times. Today, it caused the van to not be able to stop in time and the van finally came to a stop in the middle of a four way intersection. I did a Google search. There are many many people in online forums who have reported this same issue.

Acceleration or surge seemingly while transitioning from regenerative braking to friction braking. Observed numerous instances where at slower speeds, after removing my foot from the accelerator and beginning brake application, a surge or acceleration occurs. In these instances I ensured that my foot was NOT contacting the brake and accelerator simultaneously. There is a distinguishable surge in driveline when this occurs. The surge may also be caused or exacerbated by a change in driveline power (engine/battery) occurring simultaneously with the transition from regenerative to friction braking. One of the most concerning instances of the anomaly occurred while turning. When making accelerating, coordinated turn and expecting the vehicle to respond appropriately by decreasing speed, it instead momentarily accelerated. This caused great concern and a moment of panic as I had to immediately react to avoid striking other vehicles or obstacles because my intended path of travel changed as a result of this surge. Since this report of surging of the Sienna Hybrid is also reported by other owners on various forums, I’m willing to have additional sensors installed to enable ample recording of these events. This should be considered a safety event.

When applying light brake force to slow to stop for traffic light/sign the vehicle will feel like the brakes have released and stop slowing (feels like vehicle surges forward) requiring to either really apply much greater force to pedal or to release and reapply force to brake pedal to continue to slow the vehicle. Safety concern as without warning and not consistently happening additional 20 to 50 foot braking distance added to vehicle stop. Occurrence is random and happens approximately one in ten stops. The main consistency is a lower speed and gentle type stop: start braking speed generally in the 25-35mph range, brake release feel at 10-15mph range with light to medium braking force being applied. Seems to happen most often with a light downhill gradient. Occurs rendomly and cannot be reproduced on demand for service tech. Has happened since vehicle was bought new and still occurs randomly 26000 odo.

When breaking, mostly during downhill, the brakes feel like they simply “let go” for an instant. Most times this is very short and It feels like a typical downshift during breaking in an ICE car. However, last time it really gave me a lurch and I almost ended up falling off a cliff face. Many reports all over the internet but nothing from Toyota.

Intermittently, when braking to slow down towards a stop, the brakes let loose, and the vehicle surges forward for a very short spurt (like less than 1 second). While continuing to apply brake pedal pressure, the brakes, then, continue to work. This is VERY unnerving, and we are afraid that, if there were to be a pedestrian in a crosswalk in front of the vehicle they may be hit as this does cause a slightly greater braking distance overall. I reported this to my Toyota service department relatively soon after I purchased the vehicle (new), but they indicated they know nothing of the issue. I now see many people reporting this in various Internet discussion threads. This is a very serious issue.

Sometimes when each of us 2 are slowing to a stop while applying the brake, the Sienna will lunge forward. This unexpected event may cause a rear-end collision if too close. Also, it is enough to cause us to hit our head on the head rest. Can’t understand why this happening. We are sure we only have our foot on the brake and not the accelerator.