Is ESD (Electro-Static Discharge) the Culprit behind Toyota ETCS-I?

Note: This post is a subset of a posting titled “Possible Electronics Causes for Sudden Unintended Acceleration“.

Electro-Static Discharge (ESD) Issues

Electrostatic discharge (ESD) is the name given to the sudden and short-lived electric current that flows between two objects at different electrical potentials (voltages) caused by direct contact or induced by an electrostatic field. These currents, while short-lived, are unwanted that may cause damage to electronic equipment.

The simplest ESD example that people see in practice is the very brief spark that happens when during winter you  touch a metallic object, get a ‘shock’ and see a spark. (Charge develops on your body as you walk across a carpet, for example, and it gets discharged when you touch a conducting material).   More than 1KV can be generated albeit for a very short time!  At home, one often uses voltage surge suppressors to connect sensitive electronics like TVs and computers to wallpower.  Without such surge suppressors, voltage spikes like lightning can enter your electronics and cause permanent damage. Lightning, therefore, is another classic example of ESD.

Due to the damage that ESD can cause to electronics, there are military, industrial, automotive and international standards to deal with the issue. Popular consumer electronics like camcorders, mobile phones, and digital cameras have built in voltage shunts that trap these spikes from reaching the core of the electronics and damaging them.

ESD damage to electronics, which worsens over time, can fall into different categories. One, the damage can be permanent and the device fails. This is often referred to as a hard fault. Two, the damage seems to reset itself and function correctly (for a while) when the device is shut down and restarted. This is often referred to as a soft fault. Some standards even define finer distinctions.   SSUA on Toyota vehicles seems to correlate to soft faults in many cases, but in cases where a vehicle was totally wrecked, the problem could have been a hard fault.


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