* The strength and type of the magnetic field: A strong, rapidly changing magnetic field is far more likely to cause damage than a weak, static one. The frequency of the field is also a crucial factor.
* The design and shielding of the ECU: Modern ECUs often incorporate some level of electromagnetic shielding, making them more resistant to external magnetic fields. Older ECUs are generally more vulnerable.
* The duration of exposure: A brief exposure to a high magnetic field might have no effect, while prolonged exposure to even a relatively weak field could cause damage.
* The specific components within the ECU: Some components are more sensitive to magnetic fields than others.
While extremely powerful magnets (think industrial-strength electromagnets, not typical neodymium magnets) *could* potentially damage an ECU, it's unlikely a readily available magnet would achieve this. The more common way magnetic fields damage electronics is through induced currents, and this requires a *changing* magnetic field, not just a strong static one. A powerful, rapidly fluctuating magnetic field is more of a threat than a strong, constant field.
In short, there's no safe threshold. It's best to assume that exposure to strong magnetic fields could potentially damage a car computer and avoid such situations.
