I changed a thermostat in a 92 cressida and now the check engine light is on?

i changed a thermostat on a 92 cressida for these people and now thery are worried because the check engine light is on. there is two vacuum lines on the sensor on the thermostat housing
I changed a thermostat in a 92 cressida and now the check engine light is on?
are the vaccum lines connected all up to where they need to go.? if not its probably a leak in that somehow.....
I changed a thermostat in a 92 cressida and now the check engine light is on?
Dad's check engine light used to come on in his 96 Chevrolet pick up truck, we never did really figure out the exact cause, though after a while it just quit coming on, and has not came back on since. It would be a good idea to check the vacuum lines, and also check and see if it is something with the oxygen sensors as well.
disconnect the battery for 10 secs and reconnect and see if that helps