Failure sensors and check Engine does not turn on

Greetings to all here.
Which may be passing when igniting is turned on by the Normal Check Engine witness. There are bad sensors but it detects them, even disconnecting others in good condition. Any sensor that disconnects the check Engine does not turn on. It is a Nissan Sentra 95

If you could describe the engine failure, would it be easier, why is the question?

Cut cable neutral sensor, bad coolant temperature sensor, try to make failures to see if the check was caught and nothing. It is as if everything was fine.
And reality is not so. Very unstable slowdown.

Check the injectors, distributor lid and spark plug wires
that is not detected by the computer

Ok. Having if I do not explain well, my question is going to be independent if there are sensors that detects or not as it can happen. I think there must be a fault avizo when intentionally or does not disconnect or fail any sensor such as I hize (MAF, TPS, TPR, O2 sensor) In no case does the signal turn on. Could the failure be in ECU?