Help Diagnosing Unintended/Uncommanded Acceleration Issue

We have the metal rod on the UK (right-hand drive) Prius. It may have something to do with the accelerate pedal not being straight on the right-hand drive model?

 

Yes, the Prius does have a black box. It's documented in the manual. The FJ Cruiser also has a black box

 

Do you know how far back the black box data will go? Also, what all is involved if someone wants to know what the black box shows? Is it expensive and/or complicated?

 

It only keeps a few seconds. Toyota has to retrieve the data.

Tom

 

It's not like an aircraft black box, keeping hours worth of data. This device is strictly a crash record system, I'd be surprised if it buffers 10 secs before the crash

Toyota apparently needs "official" authorization before retreival

 

The system has "frame freeze" which stores the data at the last MIL.

 

The ecu freeze-frame is separate from the crash recorder box. The black box will record things like vehicle speed at time of airbag deployment, position of brake and accelerator pedal, seatbelt use yes or no, etc

 

You are in for a treat. As for the 2006, you might include a note recommending PriusChat as a good place to visit. Possibly just mark in the margins of the manual or possibly the maintenance history. <GRINS>

Bob Wilson

 

Unfortunately I have the same configuration -- 2010 V Advanced Techn -- and I am having the sudden acceleration problems and I have had the car for just two weeks. It has already happened 3 times. It appears to happen when I am braking and hitting a bump -- the car suddenly speeds up but since my foot is already on the break I just press it harder quickly and things are fine. The first two times I thought it was either my imagination or driver error but today for the 3rd time I am now convinced there is a problem.

--Steve

 

That is actually normal behavior for the Prius brake system. When you momentarily lose contact with the pavement (wheel hits bump) the Prius engages the ABS system. ABS only works with friction braking, not regenerative braking - so the "speeding up" you feel is actually the momentary loss of braking as it switches from regen to friction braking.

You will get used to it.

 

Thanks for the reply. I will try and pay more attention to it and see if that is indeed what is happening. It definitely feels like it is speeding up and not just coasting but I hear you. Yesterday when it happened I noticed that the inidicator light for wheel slippage came on and started blinking and kept blinking even when the car was completely stopped. I thought my problem might be related to a faulty traction control or other system but I have also read how that light can randomly come on even if the car is stopped. Perhaps just a coincidence but I am taking my car in for service on Tuesday.

--Steve

 

Ditto dogfriend. It feels like acceleration but it's sudden (and momentary) loss of braking.

 

What's the difference between regenerative braking and friction braking if my foot is pushing the brake pedal?

--Steve

 

The car will "simulate" brake pedal feel, while using the M/G in reverse, like a generator. Once a wheel loses traction while braking, engaging the ABS, the regenerative braking is dumped and normal brakes are used, which results in a momentary loss of braking

This schematic is for the 2004-2009 Prius

 

I had the same problem with my 2004. Every time I stopped for a light and released the brake the car would accelerate (normally) and head to Starbucks. I SWEAR,,, I don't think I was pressing the accelerator.

Kidding aside, I once did have this un-intended acceleration and it was indeed my fault. I had cleaned the car and failed to anchor the mats securely. The mat actually was pressing on the accelerator. It can be alarming the first time it happens.

 

The Prius will use regenerative braking whenever possible to try to recover some of the energy that is lost when braking. In regenerative braking, MG2 (attached directly to the wheels) acts as a generator and provides resistance to turning the wheels while generating electricity that can be stored in the battery. The Skid Control ECU communicates with the HV ECU and Battery ECU to determine how much regen braking is available and will add friction braking if necessary to slow /stop the car. Below approx 7 mph, regen does not work anymore, and the braking switches to friction only.

 

I will also support what you are being told. This is a normal quirk of the Prius. It feels like acceleration simply because you decrease the amount of braking for the same amount of foot-push and your brain sounds an alarm. It's unexpected and any change in deceleration can feel like acceleration in a relative sense. My 2 year old 2007 does this all the time on the crappy boston roads and I never notice anymore.

I do fly on airplanes almost every week and on approach to airports I frequently can't tell whether we are accelerating or just losing less speed as we descend (unless I hear engines come on and flight attendants scream )

As long as the car does not surge as you are stopping, it's just a Prius thing and part of the charm...

 

The recent Toyota recall about the gas pedals and floormats may be an attempt to address this strange event

 

I find it very disturbing and unfortunate to see how quickly certain folks immediately deny (and attack) anyone suggesting even a possibility of unintended acceleration in the Prius for no other apparent reason than they have not experienced this same symptom. They even go the point of name calling and questioning the person's honesty and integrity. I really question the intelligence of this type of behavior, as it is a true disservice to all of us. If there is a problem involving unexplained acceleration, either involving the floor mat or independent of the floor mat issue, discussion should be encouraged by all of us and these people should not be bullied or attacked for sharing their experience.

 

First the floor matt now the gas pedal. What next?