Was it your thread where I read about some previously done work suspect in skills? Could it be possible someone stuffed a meter probe into the female parts of the ECU connector and effectively made your VSS as read by the computer intermittent? Sure, swapping computers could temporarily change the condition.

One of the TB contributors learned about something like this the hard way, and has ever since been a very vocal proponent of the "drag test" which he uses where he works as an auto tech. He's looking to evaluate contact force by using a male terminal identical to the one being tested to check the tension in the female.

The reason I jumped on this was your being able to "reset" it by using the key, which is identical to the missing VSS syndrome. I don't know how many cycles it would take to raise the 311 DTC.
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Art Benstein near Baltimore

He who obtains has little. He who scatters has much. -Lao Tzu