Youlio has a high idle speed. If it is low, it will shake.

When you say OBD test port, it should be the connection port of scanning tool, right? In 2003, the OBD function has not been popularized to meet the national II emission standard.

According to your description, the tachometer is more likely to fail.

But it should not be the problem of the speed sensor, and there is probably something wrong with the instrument itself.

Your so-called speed sensor should be called crankshaft position sensor, which is located on the gearbox housing where the engine and gearbox are connected.