New sudden unintended acceleration (SUA) events – Prius Gen 3, 2011 model in UK

I experienced this for the first time in our Gen 3 last Saturday, then four times yesterday and my wife experienced it once today. I have contacted a local dealer, Jemca Toyota, who have booked the car in for a ‘diagnostics’ check in 12 days time.


I thought it might be important to post my experience here and on the Toyota Owners Club Forum, in case it happens to others, so that you may know what to expect and also in case others’ experiences can be pooled.

A brief internet search appears to show that the issue of ‘sudden unintended acceleration (SUA)’ in Toyotas and the recalls that took place, seem to have died down or become less reported since 2011. This post is also to record that it *can* still happen now and also to firmly confirm and record the independently witnessed events in my car to be absolutely nothing to do with the floormat interfering with the accelerator pedal!

Background:
Toyota Prius T-Spirit Safety Pack; Registered September 2011 (still within warrantee).
Orders for this model could only be placed for manufacture in Japan, delivery to UK was delayed because of the Tsunami. Very pleased with car. Purchased new with no problems for the last 2.5 years. Full service history with standard annual services completed and no problems.
All events below took place whilst in Eco mode. SOC ranging between 45 – 55%.
I have ScanGauge II installed, so could observe some additional information during these events.

Sudden unintended acceleration:
1. What it feels like:
The accelerator pedal drops away from your foot. You feel a gentle but firm acceleration as you are pressed into your seat. You can hear ICE revs increasing.
It is NOT like an aggressive ‘foot down’ full acceleration. It is also NOT like a gentle pulling away at lights. It is a firm, definite and insistent acceleration similar to hitting ‘RESUME’ when in cruise control or when you push up the cruise speed by 5 or 10 mph by flicking the cruise lever upwards (except that it is happening at 10 mph on an urban/city road!). It is much faster than normal acceleration in an urban/city traffic. If you do not take immediate and decisive action, a collision will certainly take place (in other words, you know you *have* to act to regain control)

2. How long it lasts:Approximately 5 seconds. Possibly up to 10 seconds (which is quite long when travelling in traffic!).
SUA is ONLY when ICE is on (i.e., never with MG1/2 driving only). ICE revs are between 1950 and 2100. Watching SGII on one occasion, it terminated as soon as coolant temp hit 60 C (which is a known ICE shutdown temperature on a Gen 3 – therefore, an ICE shutdown control signal can terminate it).

3. Controlling the car:You can overcome it (easily) by applying the footbrake. You will have to press harder than normal. It is possible at all times to control the car’s speed and bring it safety to a halt (if you want to). Slipping the car into Neutral will also work. If you go into Neutral when still moving, a yellow triangle appears on the dash display and you get a loud continuous beep alarm. This is a different behaviour to normal. Normally, if you slip the car into Neutral when moving, you do not get this alarm. This alarm can really spook your passengers! After a couple of occasions of this, I decided there was no point spooking my mother-in-law each time, so I just used the foot brake until the car stopped accelerating. I have now done this twice, with my passengers none the wiser that SUA had happened. There is therefore no need to stop the car, you can carry on driving until the SUA event stops by itself. Just stay calm and remain in control. On the observations of a link with ICE activity, I think you can abort the SUA by any method that ‘encourages’ ICE shutdown. Bringing the car to a complete stop will of course do this.

4. More details of each event:
a. April 28, 2014. Second journey of the day. Previous journey 5 hours earlier. Reversed then pulled out of a parallel parked residents bay onto a clear residential road. Reached about 10 mph when I felt SUA which took me up to about 15-20 mph before I reacted (it was my first experience). I held the speed with foot brake then slipped into Neutral. Slowed car down and pulled in to a stop with the alarm and yellow triangle going off. Switched the car off and on again. Everything back to normal for next 5 days.

b. May 1, 2014. Third journey of the day. Previous journey 30 mins before. SUA in stop-start traffic at around 10 mph. Controlled speed with footbrake. Watching SGII in the corner of my eye, saw coolant temp hit 60C, ICE shutdown and the SUA terminated while still moving in Drive.

c. May 1, 2014. Fourth journey of the day. Previous journey 2.5 hours earlier. Three SUA events on this one journey. One event was at 25-30 mph on a moderate incline. SGII showed ICE at 1950 – 2100 RPM. The car maintained its speed on this incline with my feet completely off the pedals as if I was in CC! Final event was after car was in Stage 4 (S4) of engine warm-up cycle (coolant was over 80C and SOC around 50+%).

[I removed the driver’s floormat after this journey, just to prove the point]

d. May 2, 2014. Second journey of the day. Previous journey 1 hour before. Wife was driving this time (she was passenger once before and I had primed her to know what to do). SUA started as she was slowing down to stop at a junction. Her foot was already on the footbrake, so she just pressed a little harder. As soon as stationary, ICE shutdown as expected and everything was back to normal. I was not in the car. My mother in-law was passenger and witnessed events (a) and (d).


Incidentally, my vehicle was listed under the recent Safety Recall (software fault of the Intelligent Power Module). I received my letter from VOSA about a month ago and thought I could wait till the annual service in the summer, as I have been really busy at work. When I called the dealer about the SUA, I was informed that this was ‘a separate problem’ and ‘something different’. They would conduct something that sounded like a ‘software flush’ to address the Recall issue at the same visit as this ‘diagnostics’ check. They also threatened to charge me to pay for insurance cover for the replacement vehicle, but given that the Prius is still under warrantee, I am a member of Club Toyota and am covered by Toyota Motor Insurance, I am going to try and get this negotiated away!

 

Because there are so many web postings that blame the floor mats. I had to completely eliminate this as a possibility.

To be honest, I still can't visualise how a mat lying UNDER the pedal can cause the pedal to depress. Am I missing something?

My mat was clipped in place. I'll get a photo and post it later. You will see that even if it had come off the clips it would have slipped under the bottom of the pedal. If it somehow slipped on top of the pedal, I am sure I would have felt it.

London. There probably are all kinds of installations here! The place is also crawling with Priuss (Prii?).

At this time I can't answer why, but have a suggestion (see reply below).

Yes, on each occasion when my foot was over the accelerator pedal when I happened, I felt the pedal fall away. To have a firm acceleration that activates the ICE in Eco mode (indicator to the right of the middle on the HSI), there is a lot of pedal travel and it is very noticeable.

I posted that it *felt* like when I hit RESUME on cruise control. I realise now that I never have my foot on the gas pedal when I do this, so I don't know if it moves when in C.C.

My thought or suggestion is that pedal motion *might* take place in cruise control, so there could be some sort of mechanism or actuator. I will test it the next time I am on the Motorway, which will be in about a week.

Yes, this is my second consecutive Prius. I love these cars and the level of technology they bring to the average man. You can track my postings on Priuschat over several years. I also post under the same name in Toyota Owners Club and CleanMPG. Trust me, I am not a troll and have no disclosures.

A part of my posting is exactly to say - *don't panic* if it happens to you. It is a bit surprising, but manageable. I hope that message comes through.

That is also why I am happy to wait 12 days for an appointment slot when the garage has a courtesy car. The only (slight) objection I had was when she quoted that I had to pay £10 insurance cover for the courtesy car!


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I hope you will learn to love your Prius like I and many others on this forum do.

At this time, to me, it is just a 'glitch' and a bit inconvenient because I have to take the car in when I am really busy with work commitments. It is really too early to tell what where it will go from here, but on the basis of statistics alone, you are unlikely to be affected.


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