jwriter

Hello this is for a 2001 Civic. This is kind of a technical question, but I need to know what the pulse train at the tachometer test connector looks like. In other words, what is the pulse voltage, pulse rate and pulse width, that kind of thing. My car currently doesn't have an engine, or I would just look at the signal with an oscilloscope. Probably not too many people know this but I thought I would give it a try - can anybody help?

lazlong

It pulses from 0v to around 5v. Width of the pulse depends on the vehicle speed.

jwriter

Thank you! I assume you mean engine speed. In other words, at 0 rpm the width of the pulse is vary narrow and at 6000 rpm it is much wider?

fiveten

The tach is driven by the pcm through serial communication. There is no tach pulse to measure. You can tap into the communication line with your dso and get a serial pattern but you wont know what it is saying.

lazlong

Guess I should have been more specific. The VSS signal pulses from 0v- 5v.

gabrielsousa

can you tell me how we do the wiring ?