I have a 85 mr2 157,000 miles

can you retrieve the self-diagnostic info? may have an OBD-II connector near the key, but instead will have a cryptic flashes when you turn the key to the on position...the number and sequence of the flashes will tell you....consult the guide in your owners manual~ Bring it to an autoparts store for answers. There has to be a "diagnostic" plug there under the dash or in the engine compartment~

"hydrological"....LOL~ not hydraulic?

this is pre OBD-II, theres a certain circut you have to jumper and then a light on the dash will flash a certain pattern, that would tell you what code it's throwing if any but this is too old of a car to be OBD-II OBD-I or even OBD-0

There is a little black box on the back of the engine compartment near the air cleaner. If you open the box and short lines T & E1 with the key to ON but with the engine NOT running. If there is a code set the check engine light will flash some number of times and pause. Count the number of flashes. That is the code