After years of dealing with this issue Toyota has yet to provide a reason or solution. When traveling at lower speeds the transmission disengages and when you need to accelerate there is a 1 to 2 second delay before the transmission re-engages. Toyota made me service the transmission...no help....then they claimed I needed a software update...which they charged me $80...to update their software design flaw. Still... the transmission has not improved. My only concern is that if I should ever need to accelerate to avoid an accident, my van may not respond in time.

- Greenville, NC, USA

The contact owns 2004 Toyota Sienna. The contact stated that while driving approximately 25 mph, the vehicle would not accelerate further. The vehicle was taken to an authorized dealer, where the technicians stated that the transmission fluid needed to be flushed and recalibrated. After the repairs, the failure continued. The vehicle was taken to the dealer a second time and the technicians stated that the transmission needed to be replaced. The vehicle was not repaired. The approximate failure mileage was 60,000.

- Bayonne, NJ, USA

The transmission has a delay when running at low speeds and when having to change gears up or down under a change of load condition; like going uphill or passing. Very noticeable when you take your foot off of the gas for a moment, like turning into a street or driveway. The van will jump into a gear like if someone had popped the clutch on a manual transmission. I have had this problem since I have owned the van. I have taken it the dealer several times and they always say there nothing wrong. I have had the transmission fluid changed several times but nothing changes. I thought I was the only one having this problem until just now; after reading about how many other have the same issue. I wish Toyota would just tell the truth about the vehicles that they make instead of just acting like it is always the customers who is at fault. This will be my last Toyota. I have owned three in the past, no more. Especially since all of the other things that has happen with their cars lately.

- Kingsport, TN, USA

The contact owns a 2004 Toyota Sienna.the contact stated while driving 10 mph or more the transmission would hesitate. The vehicle was taken to the dealer who stated that the transmission needed to be replaced. The current mileage was 140,000. Updated 11/05/10.

- Schaumburg, IL, USA

A 7-year old boy was climbing from the back seat to the drivers seat of a 2004 Toyota Sienna minivan. He was the only person in the van at the time, the van was not running, there were no keys in the ignition.. yet somehow, the van's transmission was taken out of park and put into gear. As the parking brake was not set, the van rolled backwards down the driveway, through a fence and into a ravine with the child inside. The child also used the steering wheel during the event (which should not be possible). No one was hurt, but damage to the vehicle and the property is extensive. It is unclear as to why the transmission and steering column lock failed on this van or if this is an isolated defect. After the accident, the transmission lock appears to be working normally.

- Topanga, CA, USA

Vsc engages at highway speeds: Vehicle alarm sounds, brakes deploy abruptly and unexpectedly, steering pulls, accelerator goes dead (pulse races, adrenaline courses). First complained to dealer after four incidents in first 20K miles: Had online testimonials of yaw sensor, steering angle sensor and ECM replacements as possible remedies; dealer rebuffed my complaints, denying service to sensors, and suggested my tires had 'gone square'. I have lived with the condition for a total of seven years. The car now 'goes off' maybe three times per every 20 miles driven, unpredictably and always shockingly. My family refuses to ride in the car. I cannot sell it in good conscience, as the defects cannot be confirmed by the dealer (and apparently therefore do not exist), so there is no way for it to be 'made safe' for a succeeding owner. Its remaining $10K+ equity has been nullified by this defect.

- Mill Valley , CA, USA

While merging onto a hwy I was leaned forward looking through the side rear view mirror with my right hand beside the seat hanging down. I raised my hand to place it on the steering wheel and my fingers caught on the shifter. The gear shift slid without resistance into reverse and the transmission shifted to reverse and started trying to go backwards. The transmission is completely wrecked and needs to be replaced. No injuries or damage to other vehicles but was a very close call as a friend was in his truck behind us and almost collided.

- Okotoks, 00, USA

Toyota 2004 Sienna. It's the most dangerous car I ever had, whenever I slow down and tend to accelerate, the car hesitate to go for about 1 to 3 seconds delay. I took it twice to the dealer but did not fix the problem, the third time I went back they denied that it is a problem. It is dangerous specially when you tend to pass a car on a two way road and the car wont accelerate at desired timing. My complain was Toyota denies that there is a problem. This problem is an ongoing since I purchased it in 2004 to present.

- San Diego, CA, USA

I have a 2004 Toyota Sienna, with only 70,000 miles. I suddenly and intermittently lost power steering. It was not total loss--that I could have handled, but it would come and go, even within a single turn. When I turned the wheel, I could not predict how the car would respond. No accident, fortunately, but a couple of close calls. I drove immediately to a T dealer, and they diagnosed a failed U joint and replaced it today. There had been no prior signs of U joint failure. I wanted to submit this in case others are experiencing similar issues. Otherwise, I just consider it an isolated case. Thanks.

- Tipp City, OH, USA

2004 Toyota Sienna xle. When accelerating the van hesitates. Have to press the accelerator harder to force a hard downshift. This is very dangerous when a predictable acceleration is needed specially merging highway.

- Ann Arbor, MI, USA

I always took my 2004 Toyota Sienna in for maintenance. The maintenance was performed by midas or Toyota. I took the vehicle in for brakes August 2008 and was told a timing belt was needed along with driving belt. I was never verbally told of a problem with the transmission. I took the vehicle back in for service to replace the timing belt, driving belt, and thermostat; still no mention of a problem with the transmission. A couple of days later the check engine light came on. When I took the vehicle back to the dealer they told me the transmission was bad and show me the dirt from the transmission. Never prior to the last visit did they verbally mention anything about a transmission problem.

- Bowie, MD, USA

Delay 2-3 seconds when press gas pedal. I though I am the only one have this problem. I hope soon Toyota can solve this problem because if I will get into and accident with this van I am going to hire a lawyer to sue the Toyota.

- Brentwood, NY, USA

There is 2 to 3 seconds delay and slight acceleration lag even when taking off from a stop. Couple of times I was close to run into accident.

- Brentwood, NY, USA

I own a 2004 Toyota Sienna with a transmission shifting problem that has been occurring since I purchased the new vehicle back in March 2003. This problem is not just on this particular vehicle as I test drove several other new vehicles from the dealer where I purchased this. The problem with the transmission is that it doesn't know when to downshift to a lower gear, particularly between 0-15 mph. When it can't decide to downshift, you can't accelerate at all. This is very dangerous when in an intersection while attempting to make a left hand turn. I made several complaints through the Toyota dealership back in 2003 and 2004. I was told that this is common with this transmission and that Toyota was going to make a software change to fix this. It has not yet been fixed and I see that they now have the same problem with the Camry. Are they going to wait until someone gets killed before they do something? action needs to be taken by Toyota to fix this issue with the Camry's and Siennas.

- Lake Wylie, SC, USA

I've seen other complaints about the transmission being hesitant and the car surging and slowing unexpectedly. I've had these problems, too. The dealership told me I needed a flash to the computer that would give the car a shift enhancement. They said it wasn't part of the powertrain warranty, but then agreed to do it for the $45 I initially paid them to look the car over. It shifts more aggressively now, but it still seems to slow and surge unexpectedly and fails to downshift for acceleration at times. Today was my first dangerous situation in which I made a left hand turn right before a curve in the road. Just as I was beginning my turn a car appeared and I had to step hard on the accelerator. The car did not respond as quickly as it should have, but I did manage to make it across.

- Tallmansville, WV, USA

Vehicle has had a transmission hesitation problem since we purchased it. The delay consists of a 2-3 second delay before the acceleration kicks in. This occurs when merging, turning or attempting to speed up to avoid collisions/objects. We have reported this problem to the dealer every time we bring it in for maintenance, with no improvement in performance. Additionally, under cruise control, the car "skips" gears unexpectedly and revvs randomly.

- Niceville, FL, USA

Vehicle hesitates when accelerator is pressed. Vehicle 'surges' at times when brake is depressed. Similar to other complaints noted in this section, my Sienna has a rough transmission, tires occasionally spin out with normal acceleration from a parking lot, toll booth, etc. Repeated trips to dealership bring no satisfaction: Response from dealer is that vehicle is operating within standards.

- Acworth, GA, USA

Toyota Sienna 2004, 19,000 miles not even 2 years old. 1. valves making noise when driving up hill at slow speed or when start driving. 2. wind noise is unacceptable. Problem begins at the very first day of driving the car. 3. one big knocking noise when the vehicle is moving, only when shift from park to D4 and starting to drive.

- Gretna, LA, USA

Transmission hesitation and lurch forward. Dealer says this is characteristic of transmission. Also, rear ac not cold - dealer says this is normal performance.

- Oak Ridge, NC, USA

Delayed engine power while turning, then sudden surge of power. Dealership response is: Working as designed - drive-by-wire causes the delay.

- Blacklick, OH, USA