Researching Toyota throttle by wire unwanted acceleration or stuck throttle cases

Doing some research on the Toyota unwanted acceleration issue.

It seems that all the cases I’ve heard of involve vehicles with a throttle that is controlled by the vehicle engine control computer instead of the old fashioned mechanical linkage. The hackaday article does a good job describing the problem. The big issue seems to be that there is no back up system to prevent a computer problem from letting this happen. A simple analog circuit that would turn off the fuel injectors if the throttle body position is above 20% open and the commanded throttle is less than 10% would be easy to do.

Look what a disaster the Boeing 737 MAX was, where a single sensor and software was allowed to crash a plane! It was caused by a very ironic situation where Boeing actually avoided having redundency in that system, because doing so would make the system appear to be a safety related system, and then it would be subject to a bunch of safety reviews and testing, causing a lot of delay.

This is from wikipedia showing what vehicles were recalled:
MY 2005–2010 Toyota Avalon
MY 2007–2010 Toyota Camry (excludes Camry Hybrid and some other models)
MY 2009–2010 Toyota Corolla*
MY 2010 Toyota Highlander* (excludes Highlander Hybrid)
MY 2009–2010 Toyota Matrix
MY 2009–2010 Toyota RAV4*
MY 2008–2010 Toyota Sequoia
MY 2007–2010 Toyota Tundra

https://en.wikipedia.org/wiki/2009%E2%80%932011_Toyota_vehicle_recalls#Field_workaround_for_sudden_unintended_acceleration

All of the above vehices appear to be throttle by wire. Vehicles with Denso pedals are excluded from the recall according to Wikipedia.

What’s interesting is that the Hybrid version of the Camry is excluded. I wonder if that’s due to a different accelerator pedal or different software? The software on a hybrid would be vastly different.

Does anyone know if a software change (including to ABS) was performed as part of the service procedure when fixing the floor mat on recalled vehicles? If so that must be how they fixed the software without actually admitting that software was the issue.

A random person once said that the Toyota computer would run out of memory and kill the throttle task, causing the throttle to be stuck at the position it was in when the throttle task was killed.

So the big question is, was it software, or a mechical issue with the throttle or floor mat? Or both? The problem with software is that it can be nearly impossible to reproduce. If 1 million Toyotas are driven today, but only 1 has a software problem, then it would be infeasable to reproduce this in a laboratory. With 1000 cars being tested, it would take 1000 days to produce a problem.

It’s strange how the issue of not being able to stop a vehicle with the brake alone never comes up. Have you ever tried putting your right foot to the floor and then tried stopping your vehicle using your left foot only, after pressing down a few times until the power brake assist goes away? It can be very difficult or impossible to do.

The whole issue can be avoided by shifting in to neutral, but there are a surprising number of people who don’t know to do this, especially under stress.

edit: This article explains everything. https://www.edn.com/toyotas-killer-firmware-bad-design-and-its-consequences/

It doesn’t look like Toyota has owned up to their dangerous software, as they went out of their way to blame floor mats and throttle pedal hardware. Neither has Boeing. I wonder if some of this had to do with corporate political correctness resulting in people working in software design who aren’t actually qualified to work on safety critical things.

If a software update wasn’t done during the recall, then these cars are still out on the road! I bet they did though, even if they sneaked it in with an ABS update or some such thing during the floor mat recall.

Since you started a new thread I’ll post this again:

Your link makes up a new cause and artificially creates a problem. Not credible.

The recalls were for the floor mat and mechanical issue with the gas pedal. No indication of reprogramming that I could find.

3 Likes

Just happened to view this comment on my newly edited in link.

Remember LaHood is the same guy who had the idea of paying people govenment money to buy new cars if they were willing to
destroy their perfectly good cars (only currently insured and operating vehicles qualified) in a program called Cash for Clunkers.

1 Like

And what was wrong with cash for clunkers? It got a lot of junk off the road.

I have performed hundreds of “floor mat” recalls.

Most recall procedures involved cutting 1 1/2" off the accelerator pedal, modification to the floor (tibia pad) and a software update to provide a fail-safe mode to close the throttle if the brake pedal is applied for more than a few seconds.

Unknown if electronic throttle body system fault detection software was tightened with the update however the production vehicles lacked the software that would stop the vehicle if the brake pedal and accelerator were applied at the same time, that is a major flaw.

Known as the “floor mat” recall, much more involved than replacing or securing the floor mat.

Safety recall 90L; RCRIT-09V388-5461.pdf (nhtsa.gov)

1 Like

Thank you! So that’s how they fixed the software on these cars. Of course the update fixed the issue where the software would let the throttle get stuck and stop responding. It’s easy to add another check in the software that would make the engine stop running if the pedal position didn’t correspond to the current amount of fuel being injected. They had to come up with a reason to get the cars in to the shop to fix this.

The throttle bodies don’t get stuck.

The software change would close the throttle if there was a conflicting input; accelerator pedal and brake pedal applied simultaneously. This protects against accelerator pedal mechanical malfunction and driver error.

Electronic malfunction is nearly impossible. The accelerator pedal and the throttle position sensors each have two sensors involved. The two sensors operate with opposite voltage inputs; 0 to 5.0 volts and 5.0 to 0 volts, if there is a correlation error, the system will shut down.

2 Likes