Should I Take Toyota's Software Update?

kiehlster writes "I'm a software developer, and I know that most software has bugs, but how much trust can we put in the many lines of code found in our automobiles? I have a 2009 Camry that is involved in both of the recent Toyota recalls. As part of the floor-mat issue, they're offering to install a software update that would cause 'the brake pedal to take precedence over the gas pedal if both were pressed,' or, as their latest notice states, 'would cut power to the engine if both pedals were pressed.' In the computer world, we're all taught to install firmware updates only if there is a real problem because a large percentage of firmware updates actually brick the hardware or cause other unforeseen consequences. On a base of 100 million lines of code, can I really trust a software update to work safely when it is delivered in a three-month development cycle? My driving habits don't cause the floor mat to slide much, so I see the update as overkill. What do you think? If it doesn't void the warranty, should I tell them to skip the update?"

Comments

Re:You're looking at it wrong.

[Rakshasa Taisab]

Good luck getting any money from Toyota or your insurance company if you _don't_ take that update.

Besides, there's not 100 million lines of code in _that_ particular part, they won't be updating your blinkenlights firmware and such at the same time.

Re:You're looking at it wrong.

[je ne sais quoi]

Not to mention that there is a real chance this isn't being caused by floor-mats or sticky pedals at all and that it's the software that's causing this in the first place. My gut is to say that their patch is necessary for the same reason why the phone company uses a program whose job it is to go and find memory that is allocated but not being used and free that memory. It's because the system is so complicated that they don't know what's causing the problem and can't find the answer, so this patch acts as a stop-gap to at least cure the symptom if not the disease.

I think you'd have to be nuts not to install it.

Re:You're looking at it wrong.

[Zurk]

IT is not THE fix. it is a failsafe for THE fix.
The REAL problem is the reading from the toyota ECM when the two redundant APP (accln pedal position) signal circuits are shorted together (main and sub), From the toyota camry VSRM :
DESCRIPTION
This ETCS (Electronic Throttle Control System) does not use a throttle cable. The Accelerator Pedal Position (APP) sensor is mounted on the accelerator pedal bracket and has 2 sensor circuits: VPA (main) and VPA2 (sub). This sensor is a non-contact type, and uses Hall-effect elements, in order to yield accurate signals, even in extreme driving conditions, such as at high speeds as well as very low speeds. The voltage, which is applied to terminals VPA and VPA2 of the ECM, varies between 0 V and 5 V in proportion to the operating angle of the accelerator pedal (throttle valve). A signal from VPA indicates the actual accelerator pedal opening angle (throttle valve opening angle) and is used for engine control. A signal from VPA2 conveys the status of the VPA circuit and is used to check the APP sensor itself. The ECM monitors the actual accelerator pedal opening angle (throttle valve opening angle) through the signals from VPA and VPA2, and controls the throttle actuator according to these signals.

FAIL-SAFE
The accelerator pedal position sensor has two (main and sub) sensor circuits. If a malfunction occurs in either of the sensor circuits, the ECM detects the abnormal signal voltage difference between the two sensor circuits and switches to limp mode. In limp mode, the functioning circuit is used to calculate the accelerator pedal opening angle to allow the vehicle to continue driving. If both circuits malfunction, the ECM regards the opening angle of the accelerator pedal as being fully closed. In this case, the throttle valve remains closed as if the engine is idling.
If a pass condition is detected and then the ignition switch is turned off, the fail-safe operation stops and the system returns to a normal condition.

VPA and VPA2 are coming from the PCM with .5-1.1v at one of the sensors and 1.2-2.0v at the other when the pedal is at its relaxed position. When there's force at the pedal, one sensor will operate between 2.6-4.5v and the other at 3.4-5.0v.

Toyota specs normal voltage for both the VPA sensors between between .4-4.8v for VPA, and .5-4.8v for VPA2 with a .2v deviation between the 2 sensors. Anything out of those ranges will trigger a DTC

An internal short could occur within one or more of the paths from the circuits leading to the ecm. That could lead to a situation where the computer cannot detect its own failure.Therefore, when the system gets conflicting information, it arbitrarily ignores half the conflicting information. It does not know which of the circuits are lying or if they both are lying and shorted together. different resistance values will lead to arbitrary acceleration. Having the brake override it is a stopgap, but ixing the real problem (perhaps with a third circuit in voting mode which will require replacing the entire circuit path) is the REAL FIX. I suspect 2012 and onwards toyotas would have a third path and faraday cage/denso replacement for the magnet assembly in the plastic accelerator pedal (which is another problem with EMI which might lead to acceleration) which i am not going to go into here.

So, YES OP you should definitely install the update. Its the only thing standing between you and death if both the APP circuits short.